Silicon carbon composites comprising ultra low z

ABSTRACT

Silicon-carbon composite materials and related processes are disclosed that overcome the challenges for providing amorphous nano-sized silicon entrained within porous carbon. Compared to other, inferior materials and processes described in the prior art, the materials and processes disclosed herein find superior utility in various applications, including energy storage devices such as lithium ion batteries.

BACKGROUND Technical Field

Embodiments of the present invention generally relate to silicon-carboncomposite materials with properties that overcome the challenges forproviding amorphous nano-sized silicon entrained within porous carbon.Said silicon-carbon composites are produced via chemical infiltrationchemical vapor infiltration to impregnate amorphous, nano-sized siliconwithin the pores of a porous scaffold. Suitable porous scaffoldsinclude, but are not limited to, porous carbon scaffolds, for examplecarbon having a pore volume comprising micropores (less than 2 nm),mesopores (2 to 50 nm), and/or macropores (greater than 50 nm). Suitableprecursors for the carbon scaffold include, but are not limited to,sugars and polyols, organic acids, phenolic compounds, cross-linkers,and amine compounds. Suitable compositing materials include, but are notlimited to, silicon materials. Precursors for the silicon include, butare not limited to, silicon containing gases such as silane, high-ordersilanes (such as di-, tri-, and/or tetrasilane), and/or chlorosilane(s)(such as mono-, di-, tri-, and tetrachlorosilane) and mixtures thereof.Chemical vapor infiltration (CVI) of silicon into the pores of porousscaffold materials is accomplished by exposing said porous scaffold tosilicon-containing gas (e.g., silane) at elevated temperatures. Theporous carbon scaffold can be a particulate porous carbon.

A key outcome in this regard is to achieve the desired form of siliconin the desired form, namely amorphous nano-sized silicon. Furthermore,another key outcome is to achieve the silicon impregnation within thepores of the porous carbon. Such materials, for example, silicon-carboncomposite materials, have utility as anode materials for energy storagedevices, for example lithium ion batteries.

Description of the Related Art

CVI is a process wherein a gaseous substrate reacts within a porousscaffold material. This approach can be employed to produce compositematerials, for instance silicon-carbon composites, wherein asilicon-containing gas decomposes at elevated temperature within aporous carbon scaffold. While this approach can be employed tomanufacture a variety of composite materials, there is particularinterest in silicon-carbon (Si—C) composite materials. Such Si—Ccomposite materials have utility, for example as energy storagematerials, for example as an anode material within a lithium ion battery(LIB). LIBs have potential to replace devices currently used in anynumber of applications. For example, current lead acid automobilebatteries are not adequate for next generation all-electric and hybridelectric vehicles due to irreversible, stable sulfate formations duringdischarge. Lithium ion batteries are a viable alternative to thelead-based systems currently used due to their capacity, and otherconsiderations.

To this end, there is continued strong interest in developing new LIBanode materials, particularly silicon, which has 10-fold highergravimetric capacity than conventional graphite. However, siliconexhibits large volume change during cycling, in turn leading toelectrode deterioration and solid-electrolyte interphase (SEI)instability. The most common amelioration approach is to reduce siliconparticle size, for instance D_(V,50)<150 nm, for instance D_(V,50)<100nm, for instance D_(V,50)<50 nm, for instance D_(V,50)<20 nm, forinstance D_(V,50)<10 nm, for instance D_(V,50)<5 nm, for instanceD_(V,50)<2 nm, either as discrete particles or within a matrix. Thusfar, techniques for creating nano-scale silicon involve high-temperaturereduction of silicon oxide, extensive particle diminution, multi-steptoxic etching, and/or other cost prohibitive processes. Likewise, commonmatrix approaches involve expensive materials such as graphene ornano-graphite, and/or require complex processing and coating.

It is known from scientific literature that non-graphitizable (hard)carbon is beneficial as a LIB anode material (Liu Y, Xue, J S, Zheng T,Dahn, J R. Carbon 1996, 34:193-200; Wu, Y P, Fang, S B, Jiang, Y Y.1998, 75:201-206; Buiel E, Dahn J R. Electrochim Acta 1999 45:121-130).The basis for this improved performance stems from the disordered natureof the graphene layers that allows Li-ions to intercalate on either sideof the graphene plane allowing for theoretically double thestoichiometric content of Li ions versus crystalline graphite.Furthermore, the disordered structure improves the rate capability ofthe material by allowing Li ions to intercalate isotropically as opposedto graphite where lithiation can only proceed in parallel to the stackedgraphene planes. Despite these desirable electrochemical properties,amorphous carbons have not seen wide-spread deployment in commercialLi-ion batteries, owing primarily to low FCE and low bulk density (<1g/cc). Instead, amorphous carbon has been used more commonly as alow-mass additive and coating for other active material components ofthe battery to improve conductivity and reduce surface side reactions.

In recent years, amorphous carbon as a LIB battery material has receivedconsiderable attention as a coating for silicon anode materials. Such asilicon-carbon core-shell structure has the potential for not onlyimproving conductivity, but also buffering the expansion of silicon asit lithiates, thus stabilizing its cycle stability and minimizingproblems associated with particle pulverization, isolation, and SEIintegrity (Jung, Y, Lee K, Oh, S. Electrochim Acta 2007 52:7061-7067;Zuo P, Yin G, Ma Y. Electrochim Acta 2007 52:4878-4883; Ng S H, Wang J,Wexler D, Chew S Y, Liu H K. J Phys Chem C 2007 111:11131-11138).Problems associated with this strategy include the lack of a suitablesilicon starting material that is amenable to the coating process, andthe inherent lack of engineered void space within the carbon-coatedsilicon core-shell composite particle to accommodate expansion of thesilicon during lithiation. This inevitably leads to cycle stabilityfailure due to destruction of core-shell structure and SEI layer(Beattie S D, Larcher D, Morcrette M, Simon B, Tarascon, J-M. JElectrochem Soc 2008 155:A158-A163).

An alternative to core shell structure is a structure wherein amorphous,nano-sized silicon is homogenously distributed within the porosity of aporous carbon scaffold. The porous carbon allows for desirableproperties: (i) carbon porosity provides void volume to accommodate theexpansion of silicon during lithiation thus reducing the net compositeparticle expansion at the electrode level; (ii) the disordered graphenenetwork provides increased electrical conductivity to the silicon thusenabling faster charge/discharge rates, (iii) nano-pore structure actsas a template for the synthesis of silicon thereby dictating its size,distribution, and morphology.

To this end, the desired inverse hierarchical structure can be achievedby employing CVI wherein a silicon-containing gas can completelypermeate nanoporous carbon and decompose therein to nano-sized silicon.The CVI approach confers several advantages in terms of siliconstructure. One advantage is that nanoporous carbon provides nucleationsites for growing silicon while dictating maximum particle shape andsize. Confining the growth of silicon within a nano-porous structureaffords reduced susceptibility to cracking or pulverization and loss ofcontact caused by expansion. Moreover, this structure promotesnano-sized silicon to remain as amorphous phase. This property providesthe opportunity for high charge/discharge rates, particularly incombination with silicon's vicinity within the conductive carbonscaffold. This system provides a high-rate-capable, solid-state lithiumdiffusion pathway that directly delivers lithium ions to the nano-scalesilicon interface. Another benefit of the silicon provide via CVI withinthe carbon scaffold is the inhibition of formation of undesirablecrystalline Li₁₅S₁₄ phase. Yet another benefit is that the CVI processprovides for void space within the particle interior.

In order to gauge relative amount of silicon impregnated into theporosity of the porous carbon, thermogravimetric analysis (TGA) may beemployed. TGA can be employed to assess the fraction of silicon residingwithin the porosity of porous carbon relative to the total siliconpresent, i.e., sum of silicon within the porosity and on the particlesurface. As the silicon-carbon composite is heated under air, the sampleexhibits a mass increase that initiates at about 300° C. to 500° C. thatreflects initial oxidation of silicon to SiO2, and then the sampleexhibits a mass loss as the carbon is burned off, and then the sampleexhibits mass increase reflecting resumed conversion of silicon intoSiO2 which increases towards an asymptotic value above 1000° C. assilicon oxidizes to completion. For purposes of this analysis, it isassumed that any mass increase above 800° C. corresponds to theoxidation of silicon to SiO2 and that the total mass at completion ofoxidation is SiO2. This allows a percentage of unoxidized silicon at800° C. as a proportion of the total amount of silicon to be determinedusing the formula:Z=1.875×[(M1100−M800)/M1100]×100%where Z is the percentage of unoxidized silicon at 800° C., M1100 is themass of the sample at completion of oxidation at a temperature of 1100°C., and M800 is the mass of the sample at 800° C. Without being bound bytheory, the temperature at which silicon is oxidized under TGAconditions relates to the length scale of the oxide coating on thesilicon due to the diffusion of oxygen atoms through the oxide layer.Thus, silicon residing within the carbon porosity will oxidize at alower temperature than deposits of silicon on a particle surface due tothe necessarily thinner coating existing on these surfaces. In thisfashion, silicon oxidation above 800° C. is used to quantitativelyassessthe fraction of silicon not impregnated within the porosity of theporous carbon scaffold.

BRIEF SUMMARY

Silicon-carbon composite materials and related processes are disclosedthat overcome the challenges for providing amorphous nano-sized siliconentrained within porous carbon. Compared to other, inferior materialsand processes described in the prior art, the materials and processesdisclosed herein find superior utility in various applications,including energy storage devices such as lithium ion batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Relationship between Z and average Coulombic efficiency forvarious silicon-carbon composite materials.

FIG. 2. Differential capacity vs voltage plot for Silicon-CarbonComposite 3 from 2^(nd) cycle using a half-cell.

FIG. 3. Differential capacity vs voltage plot for Silicon-CarbonComposite 3 from 2^(nd) cycle to 5^(th) cycle using a half-cell.

FIG. 4. dQ/dV vs V plot for various silicon-carbon composite materials.

FIG. 5. Example of Calculation of φ for Silicon-Carbon Composite 3.

FIG. 6. Z vs φ plot for various silicon-carbon composite materials.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various embodiments.However, one skilled in the art will understand that the invention maybe practiced without these details. In other instances, well-knownstructures have not been shown or described in detail to avoidunnecessarily obscuring descriptions of the embodiments. Unless thecontext requires otherwise, throughout the specification and claimswhich follow, the word “comprise” and variations thereof, such as,“comprises” and “comprising” are to be construed in an open, inclusivesense, that is, as “including, but not limited to.” Further, headingsprovided herein are for convenience only and do not interpret the scopeor meaning of the claimed invention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure or characteristicdescribed in connection with the embodiment is included in at least oneembodiment. Thus, the appearances of the phrases “in one embodiment” or“in an embodiment” in various places throughout this specification arenot necessarily all referring to the same embodiment. Furthermore, theparticular features, structures, or characteristics may be combined inany suitable manner in one or more embodiments. Also, as used in thisspecification and the appended claims, the singular forms “a,” “an,” and“the” include plural referents unless the content clearly dictatesotherwise. It should also be noted that the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

A. Porous Scaffold Materials

For the purposes of embodiments of the current invention, a porousscaffold may be used, into which silicon is to be impregnated. In thiscontext, the porous scaffold can comprise various materials. In someembodiments the porous scaffold material primarily comprises carbon, forexample hard carbon. Other allotropes of carbon are also envisioned inother embodiments, for example, graphite, amorphous carbon, diamond,C60, carbon nanotubes (e.g., single and/or multi-walled), grapheneand/or carbon fibers. The introduction of porosity into the carbonmaterial can be achieved by a variety of means. For instance, theporosity in the carbon material can be achieved by modulation of polymerprecursors, and/or processing conditions to create said porous carbonmaterial, and described in detail in the subsequent section.

In other embodiments, the porous scaffold comprises a polymer material.To this end, a wide variety of polymers are envisioned in variousembodiments to have utility, including, but not limited to, inorganicpolymer, organic polymers, and addition polymers. Examples of inorganicpolymers in this context includes, but are not limited to homochainpolymers of silicon-silicon such as polysilanes, silicon carbide,polygermanes, and polystannanes. Additional examples of inorganicpolymers includes, but are not limited to, heterochain polymers such aspolyborazylenes, polysiloxanes like polydimethylsiloxane (PDMS),polymethylhydrosiloxane (PMHS) and polydiphenylsiloxane, polysilazaneslike perhydridopolysilazane (PHPS), polyphosphazenes andpoly(dichlorophosphazenes), polyphosphates, polythiazyls, andpolysulfides. Examples of organic polymers includes, but are not limitedto, low density polyethylene (LDPE), high density polyethylene (HDPE),polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), nylon,nylon 6, nylon 6,6, teflon (Polytetrafluoroethylene), thermoplasticpolyurethanes (TPU), polyureas, poly(lactide), poly(glycolide) andcombinations thereof, phenolic resins, polyamides, polyaramids,polyethylene terephthalate, polychloroprene, polyacrylonitrile,polyaniline, polyimide, poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PDOT:PSS), and others known in the arts. The organic polymercan be synthetic or natural in origin. In some embodiments, the polymeris a polysaccharide, such as starch, cellulose, cellobiose, amylose,amylpectin, gum Arabic, lignin, and the like. In some embodiments, thepolysaccharide is derived from the carmelization of mono- or oligomericsugars, such as fructose, glucose, sucrose, maltose, raffinose, and thelike.

In certain embodiments, the porous scaffold polymer material comprises acoordination polymer. Coordination polymers in this context include, butare not limited to, metal organic frameworks (MOFs). Techniques forproduction of MOFs, as well as exemplary species of MOFs, are known anddescribed in the art (“The Chemistry and Applications of Metal-OrganicFrameworks, Hiroyasu Furukawa et al. Science 341, (2013); DOI:10.1126/science.1230444). Examples of MOFs in the context include, butare not limited to, Basolite™ materials and zeolitic imidazolateframeworks (ZIFs).

Concomitant with the myriad variety of polymers envisioned with thepotential to provide a porous substrate, various processing approachesare envisioned in various embodiments to achieve said porosity. In thiscontext, general methods for imparting porosity into various materialsare myriad, as known in the art, including, but certainly not limitedto, methods involving emulsification, micelle creation, gasification,dissolution followed by solvent removal (for example, lyophilization),axial compaction and sintering, gravity sintering, powder rolling andsintering, isostatic compaction and sintering, metal spraying, metalcoating and sintering, metal injection molding and sintering, and thelike. Other approaches to create a porous polymeric material, includingcreation of a porous gel, such as a freeze dried gel, aerogel, and thelike are also envisioned.

In certain embodiments, the porous scaffold material comprises a porousceramic material. In certain embodiments, the porous scaffold materialcomprises a porous ceramic foam. In this context, general methods forimparting porosity into ceramic materials are varied, as known in theart, including, but certainly not limited to, creation of porous In thiscontext, general methods and materials suitable for comprising theporous ceramic include, but are not limited to, porous aluminum oxide,porous zirconia toughened alumina, porous partially stabilized zirconia,porous alumina, porous sintered silicon carbide, sintered siliconnitride, porous cordierite, porous zirconium oxide, clay-bound siliconcarbide, and the like.

In certain embodiments, the porous scaffold comprises porous silica orother silicon material containing oxygen. The creation of silicon gels,including sol gels, and other porous silica materials is known in theart.

In certain embodiments, the porous material comprises a porous metal.Suitable metals in this regard include, but are not limited to porousaluminum, porous steel, porous nickel, porous Inconcel, porous Hasteloy,porous titanium, porous copper, porous brass, porous gold, poroussilver, porous germanium, and other metals capable of being formed intoporous structures, as known in the art. In some embodiments, the porousscaffold material comprises a porous metal foam. The types of metals andmethods to manufacture related to same are known in the art. Suchmethods include, but are not limited to, casting (including foaming,infiltration, and lost-foam casting), deposition (chemical andphysical), gas-eutectic formation, and powder metallurgy techniques(such as powder sintering, compaction in the presence of a foamingagent, and fiber metallurgy techniques).

B. Porous Carbon Scaffold

Methods for preparing porous carbon materials from polymer precursorsare known in the art. For example, methods for preparation of carbonmaterials are described in U.S. Pat. Nos. 7,723,262, 8,293,818,8,404,384, 8,654,507, 8,916,296, 9,269,502, 10,590,277, and U.S. patentapplication Ser. No. 16/745,197, the full disclosures of which arehereby incorporated by reference in their entireties for all purposes.

Accordingly, in one embodiment the present disclosure provides a methodfor preparing any of the carbon materials or polymer gels describedabove. The carbon materials may be synthesized through pyrolysis ofeither a single precursor, for example a saccharide material such assucrose, fructose, glucose, dextrin, maltodextrin, starch, amylopectin,amylose, lignin, gum Arabic, and other saccharides known in the art, andcombinations thereof. Alternatively, the carbon materials may besynthesized through pyrolysis of a complex resin, for instance formedusing a sol-gel method using polymer precursors such as phenol,resorcinol, bisphenol A, urea, melamine, and other suitable compoundsknown in the art, and combinations thereof, in a suitable solvent suchas water, ethanol, methanol, and other solvents known in the art, andcombinations thereof, with cross-linking agents such as formaldehyde,hexamethylenetetramine, furfural, and other cross-lining agents known inthe art, and combinations thereof. The resin may be acid or basic, andmay contain a catalyst. The catalyst may be volatile or non-volatile.The pyrolysis temperature and dwell time can vary as known in the art.

In some embodiments, the methods comprise preparation of a polymer gelby a sol gel process, condensation process or crosslinking processinvolving monomer precursor(s) and a crosslinking agent, two existingpolymers and a crosslinking agent or a single polymer and a crosslinkingagent, followed by pyrolysis of the polymer gel. The polymer gel may bedried (e.g., freeze dried) prior to pyrolysis; however drying is notnecessarily required.

The target carbon properties can be derived from a variety of polymerchemistries provided the polymerization reaction produces aresin/polymer with the necessary carbon backbone. Different polymerfamilies include novolacs, resoles, acrylates, styrenics, ureathanes,rubbers (neoprenes, styrene-butadienes, etc.), nylons, etc. Thepreparation of any of these polymer resins can occur via a number ofdifferent processes including sol gel, emulsion/suspension, solid state,solution state, melt state, etc for either polymerization andcrosslinking processes.

In some embodiments an electrochemical modifier is incorporated into thematerial as polymer. For example, the organic or carbon containingpolymer, RF for example, is copolymerized with the polymer, whichcontains the electrochemical modifier. In one embodiment, theelectrochemical modifier-containing polymer contains silicon. In oneembodiment the polymer is tetraethylorthosiliane (TEOS). In oneembodiment, a TEOS solution is added to the RF solution prior to orduring polymerization. In another embodiment the polymer is a polysilanewith organic side groups. In some cases these side groups are methylgroups, in other cases these groups are phenyl groups, in other casesthe side chains include phenyl, pyrol, acetate, vinyl, siloxanefragments. In some cases the side chain includes a group 14 element(silicon, germanium, tin or lead). In other cases the side chainincludes a group 13 element (boron, aluminum, boron, gallium, indium).In other cases the side chain includes a group 15 element (nitrogen,phosphorous, arsenic). In other cases the side chain includes a group 16element (oxygen, sulfur, selenium).

In another embodiment the electrochemical modifier comprises a silole.In some cases it is a phenol-silole or a silafluorene. In other cases itis a poly-silole or a poly-silafluorene. In some cases the silicon isreplaced with germanium (germole or germafluorene), tin (stannole orstannaflourene) nitrogen (carbazole) or phosphorous (phosphole,phosphafluorene). In all cases the heteroatom containing material can bea small molecule, an oligomer or a polymer. Phosphorous atoms may or maynot be also bonded to oxygen.

In some embodiments the reactant comprises phosphorous. In certain otherembodiments, the phosphorus is in the form of phosphoric acid. Incertain other embodiments, the phosphorus can be in the form of a salt,wherein the anion of the salt comprises one or more phosphate,phosphite, phosphide, hydrogen phosphate, dihydrogen phosphate,hexafluorophosphate, hypophosphite, polyphosphate, or pyrophosphateions, or combinations thereof. In certain other embodiments, thephosphorus can be in the form of a salt, wherein the cation of the saltcomprises one or more phosphonium ions. The non-phosphate containinganion or cation pair for any of the above embodiments can be chosen forthose known and described in the art. In the context, exemplary cationsto pair with phosphate-containing anions include, but are not limitedto, ammonium, tetraethylammonium, and tetramethylammonium ions. In thecontext, exemplary anions to pair with phosphate-containing cationsinclude, but are not limited to, carbonate, dicarbonate, and acetateions.

In some embodiments, the catalyst comprises a basic volatile catalyst.For example, in one embodiment, the basic volatile catalyst comprisesammonium carbonate, ammonium bicarbonate, ammonium acetate, ammoniumhydroxide, or combinations thereof. In a further embodiment, the basicvolatile catalyst is ammonium carbonate. In another further embodiment,the basic volatile catalyst is ammonium acetate.

In still other embodiments, the method comprises admixing an acid. Incertain embodiments, the acid is a solid at room temperature andpressure. In some embodiments, the acid is a liquid at room temperatureand pressure. In some embodiments, the acid is a liquid at roomtemperature and pressure that does not provide dissolution of one ormore of the other polymer precursors.

The acid may be selected from any number of acids suitable for thepolymerization process. For example, in some embodiments the acid isacetic acid and in other embodiments the acid is oxalic acid. In furtherembodiments, the acid is mixed with the first or second solvent in aratio of acid to solvent of 99:1, 90:10, 75:25, 50:50, 25:75, 20:80,10:90 or 1:90. In other embodiments, the acid is acetic acid and thefirst or second solvent is water. In other embodiments, acidity isprovided by adding a solid acid.

The total content of acid in the mixture can be varied to alter theproperties of the final product. In some embodiments, the acid ispresent from about 1% to about 50% by weight of mixture. In otherembodiments, the acid is present from about 5% to about 25%. In otherembodiments, the acid is present from about 10% to about 20%, forexample about 10%, about 15% or about 20%.

In certain embodiments, the polymer precursor components are blendedtogether and subsequently held for a time and at a temperaturesufficient to achieve polymerization. One or more of the polymerprecursor components can have particle size less than about 20 mm insize, for example less than 10 mm, for example less than 7 mm, forexample, less than 5 mm, for example less than 2 mm, for example lessthan 1 mm, for example less than 100 microns, for example less than 10microns. In some embodiments, the particle size of one or more of thepolymer precursor components is reduced during the blending process.

The blending of one or more polymer precursor components in the absenceof solvent can be accomplished by methods described in the art, forexample ball milling, jet milling, Fritsch milling, planetary mixing,and other mixing methodologies for mixing or blending solid particleswhile controlling the process conditions (e.g., temperature). The mixingor blending process can be accomplished before, during, and/or after (orcombinations thereof) incubation at the reaction temperature.

Reaction parameters include aging the blended mixture at a temperatureand for a time sufficient for the one or more polymer precursors toreact with each other and form a polymer. In this respect, suitableaging temperature ranges from about room temperature to temperatures ator near the melting point of one or more of the polymer precursors. Insome embodiments, suitable aging temperature ranges from about roomtemperature to temperatures at or near the glass transition temperatureof one or more of the polymer precursors. For example, in someembodiments the solvent free mixture is aged at temperatures from about20° C. to about 600° C., for example about 20° C. to about 500° C., forexample about 20° C. to about 400° C., for example about 20° C. to about300° C., for example about 20° C. to about 200° C. In certainembodiments, the solvent free mixture is aged at temperatures from about50 to about 250° C.

The reaction duration is generally sufficient to allow the polymerprecursors to react and form a polymer, for example the mixture may beaged anywhere from 1 hour to 48 hours, or more or less depending on thedesired result. Typical embodiments include aging for a period of timeranging from about 2 hours to about 48 hours, for example in someembodiments aging comprises about 12 hours and in other embodimentsaging comprises about 4-8 hours (e.g., about 6 hours).

In certain embodiments, an electrochemical modifier is incorporatedduring the above described polymerization process. For example, in someembodiments, an electrochemical modifier in the form of metal particles,metal paste, metal salt, metal oxide or molten metal can be dissolved orsuspended into the mixture from which the gel resin is produced

Exemplary electrochemical modifiers for producing composite materialsmay fall into one or more than one of the chemical classifications. Insome embodiments, the electrochemical modifier is a lithium salt, forexample, but not limited to, lithium fluoride, lithium chloride, lithiumcarbonate, lithium hydroxide, lithium benzoate, lithium bromide, lithiumformate, lithium hexafluorophosphate, lithium iodate, lithium iodide,lithium perchlorate, lithium phosphate, lithium sulfate, lithiumtetraborate, lithium tetrafluoroborate, and combinations thereof.

In certain embodiments, the electrochemical modifier comprises a metal,and exemplary species includes, but are not limited to aluminumisoproproxide, manganese acetate, nickel acetate, iron acetate, tinchloride, silicon chloride, and combinations thereof. In certainembodiments, the electrochemical modifier is a phosphate compound,including but not limited to phytic acid, phosphoric acid, ammoniumdihydrogenphosphate, and combinations thereof. In certain embodiments,the electrochemical modifier comprises silicon, and exemplary speciesincludes, but are not limited to silicon powders, silicon nanotubes,polycrystalline silicon, nanocrystalline silicon, amorphous silicon,porous silicon, nano sized silicon, nano-featured silicon, nano-sizedand nano-featured silicon, silicyne, and black silicon, and combinationsthereof.

Electrochemical modifiers can be combined with a variety of polymersystems through either physical mixing or chemical reactions with latent(or secondary) polymer functionality. Examples of latent polymerfunctionality include, but are not limited to, epoxide groups,unsaturation (double and triple bonds), acid groups, alcohol groups,amine groups, basic groups. Crosslinking with latent functionality canoccur via heteroatoms (e.g. vulcanization with sulfur, acid/base/ringopening reactions with phosphoric acid), reactions with organic acids orbases (described above), coordination to transition metals (includingbut not limited to Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ag, Au),ring opening or ring closing reactions (rotaxanes, spiro compounds,etc).

Electrochemical modifiers can also be added to the polymer systemthrough physical blending. Physical blending can include but is notlimited to melt blending of polymers and/or co-polymers, the inclusionof discrete particles, chemical vapor deposition of the electrochemicalmodifier and coprecipitation of the electrochemical modifier and themain polymer material.

In some instances the electrochemical modifier can be added via a metalsalt solid, solution, or suspension. The metal salt solid, solution orsuspension may comprise acids and/or alcohols to improve solubility ofthe metal salt. In yet another variation, the polymer gel (either beforeor after an optional drying step) is contacted with a paste comprisingthe electrochemical modifier. In yet another variation, the polymer gel(either before or after an optional drying step) is contacted with ametal or metal oxide sol comprising the desired electrochemicalmodifier.

In addition to the above exemplified electrochemical modifiers, thecomposite materials may comprise one or more additional forms (i.e.,allotropes) of carbon. In this regard, it has been found that inclusionof different allotropes of carbon such as graphite, amorphous carbon,conductive carbon, carbon black, diamond, C60, carbon nanotubes (e.g.,single and/or multi-walled), graphene and/or carbon fibers into thecomposite materials is effective to optimize the electrochemicalproperties of the composite materials. The various allotropes of carboncan be incorporated into the carbon materials during any stage of thepreparation process described herein. For example, during the solutionphase, during the gelation phase, during the curing phase, during thepyrolysis phase, during the milling phase, or after milling. In someembodiments, the second carbon form is incorporated into the compositematerial by adding the second carbon form before or duringpolymerization of the polymer gel as described in more detail herein.The polymerized polymer gel containing the second carbon form is thenprocessed according to the general techniques described herein to obtaina carbon material containing a second allotrope of carbon.

In a preferred embodiment, the carbon is produced from precursors withlittle of no solvent required for processing (solvent free). Thestructure of the polymer precursors suitable for use in a low solvent oressentially solvent free reaction mixture is not particularly limited,provided that the polymer precursor is capable of reacting with anotherpolymer precursor or with a second polymer precursor to form a polymer.Polymer precursors include amine-containing compounds,alcohol-containing compounds and carbonyl-containing compounds, forexample in some embodiments the polymer precursors are selected from analcohol, a phenol, a polyalcohol, a sugar, an alkyl amine, an aromaticamine, an aldehyde, a ketone, a carboxylic acid, an ester, a urea, anacid halide and an isocyanate.

In one embodiment employing a low or essentially solvent free reactionmixture, the method comprises use of a first and second polymerprecursor, and in some embodiments the first or second polymer precursoris a carbonyl containing compound and the other of the first or secondpolymer precursor is an alcohol containing compound. In someembodiments, a first polymer precursor is a phenolic compound and asecond polymer precursor is an aldehyde compound (e.g., formaldehyde).In one embodiment, of the method the phenolic compound is phenol,resorcinol, catechol, hydroquinone, phloroglucinol, or a combinationthereof; and the aldehyde compound is formaldehyde, acetaldehyde,propionaldehyde, butyraldehyde, benzaldehyde, cinnamaldehyde, or acombination thereof. In a further embodiment, the phenolic compound isresorcinol, phenol or a combination thereof, and the aldehyde compoundis formaldehyde. In yet further embodiments, the phenolic compound isresorcinol and the aldehyde compound is formaldehyde. In someembodiments, the polymer precursors are alcohols and carbonyl compounds(e.g., resorcinol and aldehyde) and they are present in a ratio of about0.5:1.0, respectively.

The polymer precursor materials suitable for low or essentially solventfree reaction mixture as disclosed herein include (a) alcohols, phenoliccompounds, and other mono- or polyhydroxy compounds and (b) aldehydes,ketones, and combinations thereof. Representative alcohols in thiscontext include straight chain and branched, saturated and unsaturatedalcohols. Suitable phenolic compounds include polyhydroxy benzene, suchas a dihydroxy or trihydroxy benzene. Representative polyhydroxybenzenes include resorcinol (i.e., 1,3-dihydroxy benzene), catechol,hydroquinone, and phloroglucinol. Other suitable compounds in thisregard are bisphenols, for instance, bisphenol A. Mixtures of two ormore polyhydroxy benzenes can also be used. Phenol (monohydroxy benzene)can also be used. Representative polyhydroxy compounds include sugars,such as glucose, sucrose, fructose, chitin and other polyols, such asmannitol. Aldehydes in this context include: straight chain saturatedaldehydes such as methanal (formaldehyde), ethanal (acetaldehyde),propanal (propionaldehyde), butanal (butyraldehyde), and the like;straight chain unsaturated aldehydes such as ethenone and other ketenes,2-propenal (acrylaldehyde), 2-butenal (crotonaldehyde), 3 butenal, andthe like; branched saturated and unsaturated aldehydes; andaromatic-type aldehydes such as benzaldehyde, salicylaldehyde,hydrocinnamaldehyde, and the like. Suitable ketones include: straightchain saturated ketones such as propanone and 2 butanone, and the like;straight chain unsaturated ketones such as propenone, 2 butenone, and 3butenone (methyl vinyl ketone) and the like; branched saturated andunsaturated ketones; and aromatic-type ketones such as methyl benzylketone (phenylacetone), ethyl benzyl ketone, and the like. The polymerprecursor materials can also be combinations of the precursors describedabove.

In some embodiments, one polymer precursor in the low or essentiallysolvent free reaction mixture is an alcohol-containing species andanother polymer precursor is a carbonyl-containing species. The relativeamounts of alcohol-containing species (e.g., alcohols, phenoliccompounds and mono- or poly-hydroxy compounds or combinations thereof)reacted with the carbonyl containing species (e.g. aldehydes, ketones orcombinations thereof) can vary substantially. In some embodiments, theratio of alcohol-containing species to aldehyde species is selected sothat the total moles of reactive alcohol groups in thealcohol-containing species is approximately the same as the total molesof reactive carbonyl groups in the aldehyde species. Similarly, theratio of alcohol-containing species to ketone species may be selected sothat the total moles of reactive alcohol groups in the alcoholcontaining species is approximately the same as the total moles ofreactive carbonyl groups in the ketone species. The same general 1:1molar ratio holds true when the carbonyl-containing species comprises acombination of an aldehyde species and a ketone species.

In other embodiments, the polymer precursor in the low or essentiallysolvent free reaction mixture is a urea or an amine containing compound.For example, in some embodiments the polymer precursor is urea,melamine, hexamethylenetetramine (HMT) or combination thereof. Otherembodiments include polymer precursors selected from isocyanates orother activated carbonyl compounds such as acid halides and the like.

Some embodiments of the disclosed methods include preparation of low orsolvent-free polymer gels (and carbon materials) comprisingelectrochemical modifiers. Such electrochemical modifiers include, butare not limited to nitrogen, silicon, and sulfur. In other embodiments,the electrochemical modifier comprises fluorine, iron, tin, silicon,nickel, aluminum, zinc, or manganese. The electrochemical modifier canbe included in the preparation procedure at any step. For example, insome the electrochemical modifier is admixed with the mixture, thepolymer phase or the continuous phase.

The blending of one or more polymer precursor components in the absenceof solvent can be accomplished by methods described in the art, forexample ball milling, jet milling, Fritsch milling, planetary mixing,and other mixing methodologies for mixing or blending solid particleswhile controlling the process conditions (e.g., temperature). The mixingor blending process can be accomplished before, during, and/or after (orcombinations thereof) incubation at the reaction temperature.

Reaction parameters include aging the blended mixture at a temperatureand for a time sufficient for the one or more polymer precursors toreact with each other and form a polymer. In this respect, suitableaging temperature ranges from about room temperature to temperatures ator near the melting point of one or more of the polymer precursors. Insome embodiments, suitable aging temperature ranges from about roomtemperature to temperatures at or near the glass transition temperatureof one or more of the polymer precursors. For example, in someembodiments the solvent free mixture is aged at temperatures from about20° C. to about 600° C., for example about 20° C. to about 500° C., forexample about 20° C. to about 400° C., for example about 20° C. to about300° C., for example about 20° C. to about 200° C. In certainembodiments, the solvent free mixture is aged at temperatures from about50 to about 250° C.

The porous carbon material can be achieved via pyrolysis of a polymerproduced from precursors materials as described above. In someembodiments, the porous carbon material comprises an amorphous activatedcarbon that is produced by pyrolysis, physical or chemical activation,or combination thereof in either a single process step or sequentialprocess steps.

The temperature and dwell time of pyrolysis can be varied, for examplethe dwell time van vary from 1 min to 10 min, from 10 min to 30 min,from 30 min to 1 hour, for 1 hour to 2 hours, from 2 hours to 4 hours,from 4 hours to 24 h. The temperature can be varied, for example, thepyrolysis temperature can vary from 200 to 300 C, from 250 to 350 C,from 350 C to 450 C, from 450 C to 550 C, from 540 C to 650 C, from 650C to 750 C, from 750 C to 850 C, from 850 C to 950 C, from 950 C to 1050C, from 1050 C to 1150 C, from 1150 C to 1250 C. The pyrolysis can beaccomplished in an inert gas, for example nitrogen, or argon.

In some embodiments, an alternate gas is used to further accomplishcarbon activation. In certain embodiments, pyrolysis and activation arecombined. Suitable gases for accomplishing carbon activation include,but are not limited to, carbon dioxide, carbon monoxide, water (steam),air, oxygen, and further combinations thereof. The temperature and dwelltime of activation can be varied, for example the dwell time van varyfrom 1 min to 10 min, from 10 min to 30 min, from 30 min to 1 hour, for1 hour to 2 hours, from 2 hours to 4 hours, from 4 hours to 24 h. Thetemperature can be varied, for example, the pyrolysis temperature canvary from 200 to 300 C, from 250 to 350 C, from 350 C to 450 C, from 450C to 550 C, from 540 C to 650 C, from 650 C to 750 C, from 750 C to 850C, from 850 C to 950 C, from 950 C to 1050 C, from 1050 C to 1150 C,from 1150 C to 1250 C.

Either prior to the pyrolysis, and/or after pyrolysis, and/or afteractivation, the carbon may be subjected to a particle size reduction.The particle size reduction can be accomplished by a variety oftechniques known in the art, for example by jet milling in the presenceof various gases including air, nitrogen, argon, helium, supercriticalsteam, and other gases known in the art. Other particle size reductionmethods, such as grinding, ball milling, jet milling, water jet milling,and other approaches known in the art are also envisioned.

The porous carbon scaffold may be in the form of particles. The particlesize and particle size distribution can be measured by a variety oftechniques known in the art, and can be described based on fractionalvolume. In this regard, the Dv,50 of the carbon scaffold may be between10 nm and 10 mm, for example between 100 nm and 1 mm, for examplebetween 1 um and 100 um, for example between 2 um and 50 um, examplebetween 3 um and 30 um, example between 4 um and 20 um, example between5 um and 10 um. In certain embodiments, the Dv,50 is less than 1 mm, forexample less than 100 um, for example less than 50 um, for example lessthan 30 um, for example less than 20 um, for example less than 10 um,for example less than 8 um, for example less than 5 um, for example lessthan 3 um, for example less than 1 um. In certain embodiments, theDv,100 is less than 1 mm, for example less than 100 um, for example lessthan 50 um, for example less than 30 um, for example less than 20 um,for example less than 10 um, for example less than 8 um, for exampleless than 5 um, for example less than 3 um, for example less than 1 um.In certain embodiments, the Dv,99 is less than 1 mm, for example lessthan 100 um, for example less than 50 um, for example less than 30 um,for example less than 20 um, for example less than 10 um, for exampleless than 8 um, for example less than 5 um, for example less than 3 um,for example less than 1 um. In certain embodiments, the Dv,90 is lessthan 1 mm, for example less than 100 um, for example less than 50 um,for example less than 30 um, for example less than 20 um, for exampleless than 10 um, for example less than 8 um, for example less than 5 um,for example less than 3 um, for example less than 1 um. In certainembodiments, the Dv,0 is greater than 10 nm, for example greater than100 nm, for example greater than 500 nm, for example greater than 1 um,for example greater than 2 um, for example greater than 5 um, forexample greater than 10 um. In certain embodiments, the Dv,1 is greaterthan 10 nm, for example greater than 100 nm, for example greater than500 nm, for example greater than 1 um, for example greater than 2 um,for example greater than 5 um, for example greater than 10 um. Incertain embodiments, the Dv,10 is greater than 10 nm, for examplegreater than 100 nm, for example greater than 500 nm, for examplegreater than 1 um, for example greater than 2 um, for example greaterthan 5 um, for example greater than 10 um.

In some embodiments, the surface area of the porous carbon scaffold cancomprise a surface area greater than 400 m2/g, for example greater than500 m2/g, for example greater than 750 m2/g, for example greater than1000 m2/g, for example greater than 1250 m2/g, for example greater than1500 m2/g, for example greater than 1750 m2/g, for example greater than2000 m2/g, for example greater than 2500 m2/g, for example greater than3000 m2/g. In other embodiments, the surface area of the porous carbonscaffold can be less than 500 m2/g. In some embodiments, the surfacearea of the porous carbon scaffold is between 200 and 500 m2/g. In someembodiments, the surface area of the porous carbon scaffold is between100 and 200 m2/g. In some embodiments, the surface area of the porouscarbon scaffold is between 50 and 100 m2/g. In some embodiments, thesurface area of the porous carbon scaffold is between 10 and 50 m2/g. Insome embodiments, the surface area of the porous carbon scaffold can beless than 10 m2/g.

In some embodiments, the pore volume of the porous carbon scaffold isgreater than 0.4 cm3/g, for example greater than 0.5 cm3/g, for examplegreater than 0.6 cm3/g, for example greater than 0.7 cm3/g, for examplegreater than 0.8 cm3/g, for example greater than 0.9 cm3/g, for examplegreater than 1.0 cm3/g, for example greater than 1.1 cm3/g, for examplegreater than 1.2 cm3/g, for example greater than 1.4 cm3/g, for examplegreater than 1.6 cm3/g, for example greater than 1.8 cm3/g, for examplegreater than 2.0 cm3/g. In other embodiments, the pore volume of theporous silicon scaffold is less than 0.5 cm3, for example between 0.1cm3/g and 0.5 cm3/g. In certain other embodiments, the pore volume ofthe porous silicon scaffold is between 0.01 cm3/g and 0.1 cm3/g.

In some other embodiments, the porous carbon scaffold is an amorphousactivated carbon with a pore volume between 0.2 and 2.0 cm3/g. Incertain embodiments, the carbon is an amorphous activated carbon with apore volume between 0.4 and 1.5 cm3/g. In certain embodiments, thecarbon is an amorphous activated carbon with a pore volume between 0.5and 1.2 cm3/g. In certain embodiments, the carbon is an amorphousactivated carbon with a pore volume between 0.6 and 1.0 cm3/g.

In some other embodiments, the porous carbon scaffold comprises a tapdensity of less than 1.0 g/cm3, for example less than 0.8 g/cm3, forexample less than 0.6 g/cm3, for example less than 0.5 g/cm3, forexample less than 0.4 g/cm3, for example less than 0.3 g/cm3, forexample less than 0.2 g/cm3, for example less than 0.1 g/cm3.

The surface functionality of the porous carbon scaffold can vary. Oneproperty which can be predictive of surface functionality is the pH ofthe porous carbon scaffold. The presently disclosed porous carbonscaffolds comprise pH values ranging from less than 1 to about 14, forexample less than 5, from 5 to 8 or greater than 8. In some embodiments,the pH of the porous carbon is less than 4, less than 3, less than 2 oreven less than 1. In other embodiments, the pH of the porous carbon isbetween about 5 and 6, between about 6 and 7, between about 7 and 8 orbetween 8 and 9 or between 9 and 10. In still other embodiments, the pHis high and the pH of the porous carbon ranges is greater than 8,greater than 9, greater than 10, greater than 11, greater than 12, oreven greater than 13.

The pore volume distribution of the porous carbon scaffold can vary. Forexample, the % micropores can comprise less than 30%, for example lessthan 20%, for example less than 10%, for example less than 5%, forexample less than 4%, for example less than 3%, for example less than2%, for example less than 1%, for example less than 0.5%, for exampleless than 0.2%, for example, less than 0.1%. In certain embodiments,there is no detectable micropore volume in the porous carbon scaffold.

The mesopores comprising the porous carbon scaffold can vary. Forexample, the % mesopores can comprise less than 30%, for example lessthan 20%, for example less than 10%, for example less than 5%, forexample less than 4%, for example less than 3%, for example less than2%, for example less than 1%, for example less than 0.5%, for exampleless than 0.2%, for example, less than 0.1%. In certain embodiments,there is no detectable mesopore volume in the porous carbon scaffold.

In some embodiments, the pore volume distribution of the porous carbonscaffold comprises more than 50% macropores, for example more than 60%macropores, for example more than 70% macropores, for example more than80% macropores, for example more than 90% macropores, for example morethan 95% macropores, for example more than 98% macropores, for examplemore than 99% macropores, for example more than 99.5% macropores, forexample more than 99.9% macropores.

In certain preferred embodiments, the pore volume of the porous carbonscaffold comprises a blend of micropores, mesopores, and macropores.Accordingly, in certain embodiments, the porous carbon scaffoldcomprises 0-20% micropores, 30-70% mesopores, and less than 10%macropores. In certain other embodiments, the porous carbon scaffoldcomprises 0-20% micropores, 0-20% mesopores, and 70-95% macropores. Incertain other embodiments, the porous carbon scaffold comprises 20-50%micropores, 50-80% mesopores, and 0-10% macropores. In certain otherembodiments, the porous carbon scaffold comprises 40-60% micropores,40-60% mesopores, and 0-10% macropores. In certain other embodiments,the porous carbon scaffold comprises 80-95% micropores, 0-10% mesopores,and 0-10% macropores. In certain other embodiments, the porous carbonscaffold comprises 0-10% micropores, 30-50% mesopores, and 50-70%macropores. In certain other embodiments, the porous carbon scaffoldcomprises 0-10% micropores, 70-80% mesopores, and 0-20% macropores. Incertain other embodiments, the porous carbon scaffold comprises 0-20%micropores, 70-95% mesopores, and 0-10% macropores. In certain otherembodiments, the porous carbon scaffold comprises 0-10% micropores,70-95% mesopores, and 0-20% macropores.

In certain embodiments, the % of pore volume in the porous carbonscaffold representing pores between 100 and 1000 A (10 and 100 nm)comprises greater than 30% of the total pore volume, for example greaterthan 40% of the total pore volume, for example greater than 50% of thetotal pore volume, for example greater than 60% of the total porevolume, for example greater than 70% of the total pore volume, forexample greater than 80% of the total pore volume, for example greaterthan 90% of the total pore volume, for example greater than 95% of thetotal pore volume, for example greater than 98% of the total porevolume, for example greater than 99% of the total pore volume, forexample greater than 99.5% of the total pore volume, for example greaterthan 99.9% of the total pore volume.

In certain embodiments, the pycnometry density of the porous carbonscaffold ranges from about 1 g/cc to about 3 g/cc, for example fromabout 1.5 g/cc to about 2.3 g/cc. In other embodiments, the skeletaldensity ranges from about 1.5 cc/g to about 1.6 cc/g, from about 1.6cc/g to about 1.7 cc/g, from about 1.7 cc/g to about 1.8 cc/g, fromabout 1.8 cc/g to about 1.9 cc/g, from about 1.9 cc/g to about 2.0 cc/g,from about 2.0 cc/g to about 2.1 cc/g, from about 2.1 cc/g to about 2.2cc/g or from about 2.2 cc/g to about 2.3 cc/g, from about 2.3 cc toabout 2.4 cc/g, for example from about 2.4 cc/g to about 2.5 cc/g.

C. Silicon Production Via Chemical Vapor Infiltration (CVI)

Chemical vapor deposition (CVD) is a process wherein a substrateprovides a solid surface comprising the first component of thecomposite, and the gas thermally decomposes on this solid surface toprovide the second component of composite. Such a CVD approach can beemployed, for instance, to create Si—C composite materials wherein thesilicon is coating on the outside surface of silicon particles.Alternatively, chemical vapor infiltration (CVI) is a process wherein asubstrate provides a porous scaffold comprising the first component ofthe composite, and the gas thermally decomposes on into the porosity(into the pores) of the porous scaffold material to provide the secondcomponent of composite.

In an embodiment, silicon is created within the pores of the porouscarbon scaffold by subjecting the porous carbon particles to a siliconcontaining precursor gas at elevated temperature and the presence of asilicon-containing gas, preferably silane, in order to decompose saidgas into silicon. The silicon containing precursor gas can be mixed withother inert gases, for example, nitrogen gas. The temperature and timeof processing can be varied, for example the temperature can be between200 and 900 C, for example between 200 and 250 C, for example between250 and 300 C, for example between 300 and 350 C, for example between300 and 400 C, for example between 350 and 450 C, for example between350 and 400 C, for example between 400 and 500 C, for example between500 and 600 C, for example between 600 and 700 C, for example between700 and 800 C, for example between 800 and 900 C, for example between600 and 1100 C.

The mixture of gas can comprise between 0.1 and 1% silane and remainderinert gas. Alternatively, the mixture of gas can comprise between 1% and10% silane and remainder inert gas. Alternatively, the mixture of gascan comprise between 10% and 20% silane and remainder inert gas.Alternatively, the mixture of gas can comprise between 20% and 50%silane and remainder inert gas. Alternatively, the mixture of gas cancomprise above 50% silane and remainder inert gas. Alternatively, thegas can essentially be 100% silane gas. Suitable inert gases include,but are not limited to, hydrogen, nitrogen, argon, and combinationsthereof.

The pressure for the CVI process can be varied. In some embodiments, thepressure is atmospheric pressure. In some embodiments, the pressure isbelow atmospheric pressure. In some embodiments, the pressure is aboveatmospheric pressure.

C. Physico- and Electrochemical Properties of Silicon-Carbon Composite

While not wishing to be bound by theory, it is believed that the nanosized silicon achieved as a result of filling in certain, desired porevolume structure of the porous carbon scaffold (for instance, siliconfilling pores in the range of 5 to 1000 nm, or other range as disclosedelsewhere herein), along with the advantageous properties of the othercomponents of the composite, including low surface area, low pycnometrydensity, yield composite materials having different and advantageousproperties, for instance electrochemical performance when the compositecomprises an anode of a lithium ion energy storage device.

In certain embodiments, the embedded silicon particles embedded withinthe composite comprise nano-sized features. The nano-sized features canhave a characteristic length scale of preferably less than 1 um,preferably less than 300 nm, preferably less than 150 nm, preferablyless than 100 um, preferably less than 50 nm, preferably less than 30nm, preferably less than 15 nm, preferably less than 10 nm, preferablyless than 5 nm.

In certain embodiments, the silicon embedded within the composite isspherical in shape. In certain other embodiments, the porous siliconparticles are non-spherical, for example rod-like, or fibrous instructure. In some embodiments, the silicon exists as a layer coatingthe inside of pores within the porous carbon scaffold. The depth of thissilicon layer can vary, for example the depth can between 5 nm and 10nm, for example between 5 nm and 20 nm, for example between 5 nm and 30nm, for example between 5 nm and 33 nm, for example between 10 nm and 30nm, for example between 10 nm and 50 nm, for example between 10 nm and100 nm, for example between 10 and 150 nm, for example between 50 nm and150 nm, for example between 100 and 300 nm, for example between 300 and1000 nm.

In some embodiments, the silicon embedded within the composite is nanosized, and resides within pores of the porous carbon scaffold. Forexample, the embedded silicon can be impregnated, deposited by CVI, orother appropriate process into pores within the porous carbon particlecomprising pore sizes between 5 and 1000 nm, for example between 10 and500 nm, for example between 10 and 200 nm, for example between 10 and100 nm, for example between 33 and 150 nm, for example between and 20and 100 nm. Other ranges of carbon pores sizes with regards tofractional pore volume, whether micropores, mesopores, or macropores,are also envisioned.

Embodiments of the composite with extremely durable intercalation oflithium disclosed herein improves the properties of any number ofelectrical energy storage devices, for example lithium ion batteries. Insome embodiments, the silicon-carbon composite disclosed herein exhibitsa Z less than 5, for example a Z less than 4, for example a Z less than3, for example a Z less than 2, for example a Z less than 1, for examplea Z less than 0.1, for example a Z less than 0.01, for example a Z lessthan 0.001. In certain embodiments, the Z is essentially zero. Incertain embodiments, the Z has a negative value, i.e., M800>M1100.

In certain preferred embodiment, the silicon-carbon composite comprisesdesirably low Z in combination with another desired physicochemicaland/or electrochemical property or in combination with more than oneother desired physicochemical and/or electrochemical properties. Table 1provides a description of certain embodiments for combination ofproperties for the silicon-carbon composite.

TABLE 1 Embodiments for silicon-carbon composite with embodiedproperties. In some embodiments the silicon-carbon composite comprises .. . Z <5, <4, <3, <2, <1, <0.1, <0.01, <0.01, 0, negative value; SurfaceArea <100 m2/g, <50 m2/g, <30 m2/g, <20 m2/g, <10 m2/g, <5 m2/g, <4m2/g, <3 m2/g, <2 m2/g, <1 m2/g; FirstCycle >75%, >80%, >85%, >90%, >91%, >92%, >93%,Efficiency >94%, >95%, >96%, >97%, >98%, >99%; Reversible >1300mAh/g, >1600 mAh/g, >1700 mAh/g, Capacity >1800 mAh/g, >1900mAh/g, >2000 mAh/g, >2100 mAh/g, >2200 mAh/g, >2300 mAh/g, >2400mAh/g, >2500 mAh/g, >2600 mAh/g, >2700 mAh/g, >2800 mAh/g, >2900mAh/g, >3000 mAh/g; and/or Silicon Content 10%-90%, 15-85%, 20%-80%,30%-70%, by weight 40%-60%.

According to Table 1, the silicon-carbon composite may comprisecombinations of various properties. For example, the silicon-carboncomposite may comprise a Z less than 4, surface area less than 100 m2/g,a first cycle efficiency greater than 80%, and a reversible capacity ofat least 1300 mAh/g. For example, the silicon-carbon composite maycomprise a Z less than 4, surface area less than 100 m2/g, a first cycleefficiency greater than 80%, and a reversible capacity of at least 1600mAh/g. For example, the silicon-carbon composite may comprise a Z lessthan 4, surface area less than 20 m2/g, a first cycle efficiency greaterthan 85%, and a reversible capacity of at least 1600 mAh/g. For example,the silicon-carbon composite may comprise a Z less than 4, surface arealess than 10 m2/g, a first cycle efficiency greater than 85%, and areversible capacity of at least 1600 mAh/g. For example, thesilicon-carbon composite may comprise a Z less than 4, surface area lessthan 10 m2/g, a first cycle efficiency greater than 90%, and areversible capacity of at least 1600 mAh/g. For example, thesilicon-carbon composite may comprise a Z less than 4, surface area lessthan 10 m2/g, a first cycle efficiency greater than 90%, and areversible capacity of at least 1800 mAh/g.

The silicon-carbon composite can comprise a combination of theaforementioned properties, in addition to also comprising a carbonscaffold comprising properties also described within this proposal.Accordingly, Table 2 provides a description of certain embodiments forcombination of properties for the silicon-carbon composite.

TABLE 2 Embodiments for silicon-carbon composite with embodiedproperties. In some embodiments the silicon-carbon composite comprises .. . Z <5, <4, <3, <2, <1, <0.1, <0.01, <0.01, 0, negative value; SurfaceArea <100 m2/g, <50 m2/g, <30 m2/g, <20 m2/g, <10 m2/g, <5 m2/g, <4m2/g, <3 m2/g, <2 m2/g, <1 m2/g; FirstCycle >75%, >80%, >85%, >90%, >91%, >92%, >93%,Efficiency >94%, >95%, >96%, >97%, >98%, >99%; Reversible >1300mAh/g, >1600 mAh/g, >1700 mAh/g, Capacity >1800 mAh/g, >1900mAh/g, >2000 mAh/g, >2100 mAh/g, >2200 mAh/g, >2300 mAh/g, >2400mAh/g, >2500 mAh/g, >2600 mAh/g, >2700 mAh/g, >2800 mAh/g, >2900mAh/g, >3000 mAh/g; Silicon Content 10%-90%, 15-85%, 20%-80%, 30%-70%,by weight 40%-60%; Carbon Scaffold 0.1-1.5 cm3/g, 0.2-1.2 cm3/g, 0.3-1.1cm3/g, pore volume 0.4-1.0 cm3/g, 0.4-1.0 cm3/g, 0.5-1.0 cm3/g, 0.6-1.0cm3/g, 0.5-0.9 cm3/g, 0.4-1.0 cm3/g, >0.1 cm3/g, >0.2 cm3/g, >0.4cm3/g, >0.6 cm3/g, >0.8 cm3/g; % silicon 15%-25%, 25%-35%, 20%-40%,25%-50%, content 30%-70%, 30%-60%, 60%-80%, 80%-100%; Scaffold pore <1nm, 1-5 nm, 5-1000 nm, 10-500 nm, 10-200 nm, size range 10-100 nm,33-150 nm, 20-100 nm; and/or Percentage of >20%/>30%/>30%, <10/>30/>30,<5/>30/>30, microporosity/ <5/>40/>40, <1/>40/>40, <10/>70/>20,<10/>20/>70, mesoporosity/ >10/>10/>80, <10/>80/>10, <5/>70/>20,<5/>20/>70, macroporosity <5/>5/>80, <5/>80/>10, >80%/<20%/<20%,expressed as >70/<30/<10, >70/<30/<5, >70/<20/<10, >70/<10/<10,percentage of >70/<10/<5, >70/<5/<5, >80/<20/<10, >80/<20/<5, totalpore >80/<20/<1, >80/<10/<10, >80/<10/<5, >80/<10/<1,volume >90/<10/<10, >90/<10/<5, >90/<10/<1, >90/<5/<1, >95/<5/<5,>90/<5/<1

As used in herein, the percentage “microporosity,” “mesoporosity” and“macroporosity” refers to the percent of micropores, mesopores andmacropores, respectively, as a percent of total pore volume. Forexample, a carbon scaffold having 90% microporosity is a carbon scaffoldwhere 90% of the total pore volume of the carbon scaffold is formed bymicropores.

According to Table 2, the silicon-carbon composite may comprisecombinations of various properties. For example, the silicon-carboncomposite may comprise a Z less than 4, surface area less than 100 m2/g,a first cycle efficiency greater than 80%, a reversible capacity of atleast 1600 mAh/g, a silicon content of 15%-85%, a carbon scaffold totalpore volume of 0.2-1.2 cm3/g wherein the scaffold pore volumecomprises >80% micropores, <20% mesopores, and <10% macropores. Forexample, the silicon-carbon composite may comprise a Z less than 4,surface area less than 20 m2/g, a first cycle efficiency greater than85%, and a reversible capacity of at least 1600 mAh/g, a silicon contentof 15%-85%, a carbon scaffold total pore volume of 0.2-1.2 cm3/g whereinthe scaffold pore volume comprises >80% micropores, <20% mesopores, and<10% macropores. For example, the silicon-carbon composite may comprisea Z less than 4, surface area less than 10 m2/g, a first cycleefficiency greater than 85%, and a reversible capacity of at least 1600mAh/g, a silicon content of 15%-85%, a carbon scaffold total pore volumeof 0.2-1.2 cm3/g wherein the scaffold pore volume comprises >80%micropores, <20% mesopores, and <10% macropores. For example, thesilicon-carbon composite may comprise a Z less than 4, surface area lessthan 10 m2/g, a first cycle efficiency greater than 90%, and areversible capacity of at least 1600 mAh/g, a silicon content of15%-85%, a carbon scaffold total pore volume of 0.2-1.2 cm3/g whereinthe scaffold pore volume comprises >80% micropores, <20% mesopores, and<10% macropores. For example, the silicon-carbon composite may comprisea Z less than 4, surface area less than 10 m2/g, a first cycleefficiency greater than 90%, and a reversible capacity of at least 1800mAh/g, a silicon content of 15%-85%, a carbon scaffold total pore volumeof 0.2-1.2 cm3/g wherein the scaffold pore volume comprises >80%micropores, <20% mesopores, and <10% macropores.

Without being bound by theory, the filling of silicon within the poresof the porous carbon traps porosity within the porous carbon scaffoldparticle, resulting in inaccessible volume, for example volume that isinaccessible to nitrogen gas. Accordingly, the silicon-carbon compositematerial may exhibit a pycnometry density of less than 2.1 g/cm3, forexample less than 2.0 g/cm3, for example less than 1.9 g/cm3, forexample less than 1.8 g/cm3, for example less than 1.7 g/cm3, forexample less than 1.6 g/cm3, for example less than 1.4 g/cm3, forexample less than 1.2 g/cm3, for example less than 1.0 g/cm3.

The pore volume of the composite material exhibiting extremely durableintercalation of lithium can range between 0.01 cm3/g and 0.2 cm3/g. Incertain embodiments, the pore volume of the composite material can rangebetween 0.01 cm3/g and 0.15 cm3/g, for example between 0.01 cm3/g and0.1 cm3/g, for example between 0.01 cm3/g and 0.05 cm2/g.

The particle size distribution of the composite material exhibitingextremely durable intercalation of lithium is important to bothdetermine power performance as well as volumetric capacity. As thepacking improves, the volumetric capacity may increase. In oneembodiment the distributions are either Gaussian with a single peak inshape, bimodal, or polymodal (>2 distinct peaks, for example trimodal).The properties of particle size of the composite can be described by theDO (smallest particle in the distribution), Dv50 (average particle size)and Dv100 (maximum size of the largest particle). The optimal combinedof particle packing and performance will be some combination of the sizeranges below. The particle size reduction in the such embodiments can becarried out as known in the art, for example by jet milling in thepresence of various gases including air, nitrogen, argon, helium,supercritical steam, and other gases known in the art.

In one embodiment the Dv0 of the composite material can range from 1 nmto 5 microns. In another embodiment the Dv0 of the composite ranges from5 nm to 1 micron, for example 5-500 nm, for example 5-100 nm, forexample 10-50 nm. In another embodiment the Dv0 of the composite rangesfrom 500 nm to 2 microns, or 750 nm to 1 um, or 1-2 um. microns to 2microns. In other embodiments, the Dv0 of the composite ranges from 2-5um, or >5 um.

In some embodiments the Dv50 of the composite material ranges from 5 nmto 20 um. In other embodiments the Dv50 of the composite ranges from 5nm to 1 um, for example 5-500 nm, for example 5-100 nm, for example10-50 nm. In another embodiment the Dv50 of the composite ranges from500 nm to 2 um, 750 nm to 1 um, 1-2 um. In still another embodiments,the Dv50 of the composite ranges from 1 to 1000 um, for example from1-100 um, for example from 1-10 um, for example 2-20 um, for example3-15 um, for example 4-8 um. In certain embodiments, the Dv50 is >20 um,for example >50 um, for example >100 um.

The span (Dv50)/(Dv90-Dv10), wherein Dv10, Dv50 and Dv90 represent theparticle size at 10%, 50%, and 90% of the volume distribution, can bevaried from example from 100 to 10, from 10 to 5, from 5 to 2, from 2 to1; in some embodiments the span can be less than 1. In certainembodiments, the composite comprising carbon and porous silicon materialparticle size distribution can be multimodal, for example, bimodal, ortrimodal.

The surface functionality of the presently disclosed the compositematerial exhibiting extremely durable intercalation of lithium may bealtered to obtain the desired electrochemical properties. One propertywhich can be predictive of surface functionality is the pH of thecomposite materials. The presently disclosed composite materialscomprise pH values ranging from less than 1 to about 14, for exampleless than 5, from 5 to 8 or greater than 8. In some embodiments, the pHof the composite materials is less than 4, less than 3, less than 2 oreven less than 1. In other embodiments, the pH of the compositematerials is between about 5 and 6, between about 6 and 7, between about7 and 8 or between 8 and 9 or between 9 and 10. In still otherembodiments, the pH is high and the pH of the composite materials rangesis greater than 8, greater than 9, greater than 10, greater than 11,greater than 12, or even greater than 13.

The silicon-carbon composite material may comprise varying amounts ofcarbon, oxygen, hydrogen and nitrogen as measured by gas chromatographyCHNO analysis. In one embodiment, the carbon content of the composite isgreater than 98 wt. % or even greater than 99.9 wt % as measured by CHNOanalysis. In another embodiment, the carbon content of thesilicon-carbon composite ranges from about 10-90%, for example 20-80%,for example 30-70%, for example 40-60%.

In some embodiments, silicon-carbon composite material comprises anitrogen content ranging from 0-90%, example 0.1-1%, for example 1-3%,for example 1-5%, for example 1-10%, for example 10-20%, for example20-30%, for example 30-90%.

In some embodiments, the oxygen content ranges from 0-90%, example0.1-1%, for example 1-3%, for example 1-5%, for example 1-10%, forexample 10-20%, for example 20-30%, for example 30-90%.

The silicon-carbon composite material may also incorporate anelectrochemical modifier selected to optimize the electrochemicalperformance of the non-modified composite. The electrochemical modifiermay be incorporated within the pore structure and/or on the surface ofthe porous carbon scaffold, within the embedded silicon, or within thefinal layer of carbon, or conductive polymer, coating, or incorporatedin any number of other ways. For example, in some embodiments, thecomposite materials comprise a coating of the electrochemical modifier(e.g., silicon or Al₂O₃) on the surface of the carbon materials. In someembodiments, the composite materials comprise greater than about 100 ppmof an electrochemical modifier. In certain embodiments, theelectrochemical modifier is selected from iron, tin, silicon, nickel,aluminum and manganese.

In certain embodiments the electrochemical modifier comprises an elementwith the ability to lithiate from 3 to 0 V versus lithium metal (e.g.silicon, tin, sulfur). In other embodiments, the electrochemicalmodifier comprises metal oxides with the ability to lithiate from 3 to 0V versus lithium metal (e.g. iron oxide, molybdenum oxide, titaniumoxide). In still other embodiments, the electrochemical modifiercomprises elements which do not lithiate from 3 to 0 V versus lithiummetal (e.g. aluminum, manganese, nickel, metal-phosphates). In yet otherembodiments, the electrochemical modifier comprises a non-metal element(e.g. fluorine, nitrogen, hydrogen). In still other embodiments, theelectrochemical modifier comprises any of the foregoing electrochemicalmodifiers or any combination thereof (e.g. tin-silicon, nickel-titaniumoxide).

The electrochemical modifier may be provided in any number of forms. Forexample, in some embodiments the electrochemical modifier comprises asalt. In other embodiments, the electrochemical modifier comprises oneor more elements in elemental form, for example elemental iron, tin,silicon, nickel or manganese. In other embodiments, the electrochemicalmodifier comprises one or more elements in oxidized form, for exampleiron oxides, tin oxides, silicon oxides, nickel oxides, aluminum oxidesor manganese oxides.

The electrochemical properties of the composite material can bemodified, at least in part, by the amount of the electrochemicalmodifier in the material, wherein the electrochemical modifier is analloying material such as silicon, tin, indium, aluminum, germanium,gallium. Accordingly, in some embodiments, the composite materialcomprises at least 0.10%, at least 0.25%, at least 0.50%, at least 1.0%,at least 5.0%, at least 10%, at least 25%, at least 50%, at least 75%,at least 90%, at least 95%, at least 99% or at least 99.5% of theelectrochemical modifier.

The particle size of the composite material may expand upon lithiationas compared to the non-lithiated state. For example, the expansionfactor, defined as ratio of the average particle size of particles ofcomposite material comprising a porous silicon material upon lithiationdivided by the average particle size under non-lithiated conditions. Asdescribed in the art, this expansion factor can be relatively large forpreviously known, non-optimal silicon-containing materials, for exampleabout 4× (corresponding to a 400% volume expansion upon lithiation). Thecurrent inventors have discovered composite materials comprising aporous silicon material that can exhibit a lower extent of expansion,for example, the expansion factor can vary from 3.5 to 4, from 3.0 to3.5, from 2.5 to 3.0, from 2.0 to 2.5, from 1.5 to 2.0, from 1.0 to 1.5.

It is envisioned that composite materials in certain embodiments willcomprise a fraction of trapped pore volume, namely, void volumenon-accessible to nitrogen gas as probed by nitrogen gas sorptionmeasurement. Without being bound by theory, this trapped pore volume isimportant in that it provides volume into which silicon can expand uponlithiation.

In certain embodiments, the ratio of trapped void volume to the siliconvolume comprising the composite particle is between 0.1:1 and 10:1. Forexample, the ratio of trapped void volume to the silicon volumecomprising the composite particle is between 1:1 and 5:1, or 5:1 to10:1. In embodiments, the ratio of ratio trapped void volume to thesilicon volume comprising the composite particle is between 2:1 and 5:1,or about 3:1, in order to efficiently accommodate the maximum extent ofexpansion of silicon upon lithiation.

In certain embodiments, the electrochemical performance of the compositedisclosed herein is tested in a half-cell; alternatively the performanceof the composite with extremely durable intercalation of lithiumdisclosed herein is tested in a full cell, for example a full cell coincell, a full cell pouch cell, a prismatic cell, or other batteryconfigurations known in the art. The anode composition comprising thecomposite with extremely durable intercalation of lithium disclosedherein can further comprise various species, as known in the art.Additional formulation components include, but are not limited to,conductive additives, such as conductive carbons such as Super C45,Super P, Ketjenblack carbons, and the like, conductive polymers and thelike, binders such as styrene-butadiene rubber sodiumcarboxymethylcellulose (SBR-Na-CMC), polyvinylidene difluoride (PVDF),polyimide (PI), polyacrylic acid (PAA) and the like, and combinationsthereof. In certain embodiments, the binder can comprise a lithium ionas counter ion.

Other species comprising the electrode are known in the art. The % ofactive material in the electrode by weight can vary, for example between1 and 5%, for example between 5 and 15%, for example between 15 and 25%,for example between 25 and 35%, for example between 35 and 45%, forexample between 45 and 55%, for example between 55 and 65%, for examplebetween 65 and 75%, for example between 75 and 85%, for example between85 and 95%. In some embodiments, the active material comprises between80 and 95% of the electrode. In certain embodiment, the amount ofconductive additive in the electrode can vary, for example between 1 and5%, between 5 and 15%, for example between 15 and 25%, for examplebetween 25 and 35%. In some embodiments, the amount of conductiveadditive in the electrode is between 5 and 25%. In certain embodiments,the amount of binder can vary, for example between 1 and 5%, between 5and 15%, for example between 15 and 25%, for example between 25 and 35%.In certain embodiments, the amount of conductive additive in theelectrode is between 5 and 25%.

The silicon-carbon composite material may be prelithiated, as known inthe art. In certain embodiments, the prelithiation is achievedelectrochemically, for example in a half cell, prior to assembling thelithiated anode comprising the porous silicon material into a full celllithium ion battery. In certain embodiments, prelithiation isaccomplished by doping the cathode with a lithium-containing compound,for example a lithium containing salt. Examples of suitable lithiumsalts in this context include, but are not limited to, dilithiumtetrabromonickelate(II), dilithium tetrachlorocuprate(II), lithiumazide, lithium benzoate, lithium bromide, lithium carbonate, lithiumchloride, lithium cyclohexanebutyrate, lithium fluoride, lithiumformate, lithium hexafluoroarsenate(V), lithium hexafluorophosphate,lithium hydroxide, lithium iodate, lithium iodide, lithium metaborate,lithium perchlorate, lithium phosphate, lithium sulfate, lithiumtetraborate, lithium tetrachloroaluminate, lithium tetrafluoroborate,lithium thiocyanate, lithium trifluoromethanesulfonate, lithiumtrifluoromethanesulfonate, and combinations thereof.

The anode comprising the silicon-carbon composite material can be pairedwith various cathode materials to result in a full cell lithium ionbattery. Examples of suitable cathode materials are known in the art.Examples of such cathode materials include, but are not limited toLiCoO₂ (LCO), LiNi_(0.8)Co_(0.15)Al_(0.05)O₂ (NCA),LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ (NMC), LiMn₂O₄ and variants (LMO), andLiFePO₄ (LFP).

For the full cell lithium ion battery comprising an anode furthercomprising the silicon-carbon composite material, pairing of cathode toanode can be varied. For example, the ratio of cathode-to-anode capacitycan vary from 0.7 to 1.3. In certain embodiments, the ratio ofcathode-to-anode capacity can vary from 0.7 to 1.0, for example from 0.8to 1.0, for example from 0.85 to 1.0, for example from 0.9 to 1.0, forexample from 0.95 to 1.0. In other embodiments, the ratio ofcathode-to-anode capacity can vary from 1.0 to 1.3, for example from 1.0to 1.2, for example from 1.0 to 1.15, for example from 1.0 to 1.1, forexample from 1.0 to 1.05. In yet other embodiments, the ratio ofcathode-to-anode capacity can vary from 0.8 to 1.2, for example from 0.9to 1.1, for example from 0.95 to 1.05.

For the full cell lithium ion battery comprising an anode furthercomprising the silicon-carbon composite material, the voltage window forcharging and discharging can be varied. In this regard, the voltagewindow can be varied as known in the art, depending on variousproperties of the lithium ion battery. For instance, the choice ofcathode plays a role in the voltage window chosen, as known in the art.Examples of voltage windows vary, for example, in terms of potentialversus Li/Li+, from 2.0 V to 5.0 V, for example from 2.5 V to 4.5V, forexample from 2.5V to 4.2V.

For the full cell lithium ion battery comprising an anode furthercomprising the silicon-carbon composite material, the strategy forconditioning the cell can be varied as known in the art. For example,the conditioning can be accomplished by one or more charge and dischargecycles at various rate(s), for example at rates slower than the desiredcycling rate. As known in the art, the conditioning process may alsoinclude a step to unseal the lithium ion battery, evacuate any gasesgenerated within during the conditioning process, followed by resealingthe lithium ion battery.

For the full cell lithium ion battery comprising an anode furthercomprising the silicon-carbon composite material, the cycling rate canbe varied as known in the art, for example, the rate can between C/20and 20 C, for example between C10 to 10 C, for example between C/5 and 5C. In certain embodiments, the cycling rate is C/10. In certainembodiments, the cycling rate is C/5. In certain embodiments, thecycling rate is C/2. In certain embodiments, the cycling rate is 1 C. Incertain embodiments, the cycling rate is 1 C, with periodic reductionsin the rate to a slower rate, for example cycling at 1 C with a C/10rate employed every 20^(th) cycle. In certain embodiments, the cyclingrate is 2 C. In certain embodiments, the cycling rate is 4 C. In certainembodiments, the cycling rate is 5 C. In certain embodiments, thecycling rate is 10 C. In certain embodiments, the cycling rate is 20 C.

The first cycle efficiency of the composite with extremely durableintercalation of lithium disclosed herein be determined by comparing thelithium inserted into the anode during the first cycle to the lithiumextracted from the anode on the first cycle, prior prelithiationmodification. When the insertion and extraction are equal, theefficiency is 100%. As known in the art, the anode material can betested in a half-cell, where the counter electrode is lithium metal, theelectrolyte is a 1M LiPF₆ 1:1 ethylene carbonate:diethylcarbonate(EC:DEC), using a commercial polypropylene separator. In certainembodiments, the electrolyte can comprise various additives known toprovide improved performance, such as fluoroethylene carbonate (FEC) orother related fluorinated carbonate compounds, or ester co-solvents suchas methyl butyrate, vinylene carbonate, and other electrolyte additivesknown to improve electrochemical performance of silicon-comprising anodematerials.

Coulombic efficiency can be averaged, for example averaged over cycles 7to cycle 25 when tested in a half cell. Coulombic efficiency can beaveraged, for example averaged over cycles 7 to cycle 20 when tested ina half cell. In certain embodiments, the average efficiency of thecomposite with extremely durable intercalation of lithium is greaterthan 0.9, or 90%. In certain embodiments, the average efficiency isgreater than 0.95, or 95%. In certain other embodiments, the averageefficiency is 0.99 or greater, for example 0.991 or greater, for example0.992 or greater, for example 0.993 or greater, for example 0.994 orgreater, for example 0.995 or greater, for example 0.996 or greater, forexample 0.997 or greater, for example 0.998 or greater, for example0.999 or greater, for example 0.9991 or greater, for example 0.9992 orgreater, for example 0.9993 or greater, for example 0.9994 or greater,for example 0.9995 or greater, for example 0.9996 or greater, forexample 0.9997 or greater, for example 0.9998 or greater, for example0.9999 or greater.

In still other embodiments the present disclosure provides a compositematerial exhibiting extremely durable intercalation of lithium, whereinwhen the composite material is incorporated into an electrode of alithium-based energy storage device the composite material has avolumetric capacity at least 10% greater than when the lithium basedenergy storage device comprises a graphite electrode. In someembodiments, the lithium based energy storage device is a lithium ionbattery. In other embodiments, the composite material has a volumetriccapacity in a lithium-based energy storage device that is at least 5%greater, at least 10% greater, at least 15% greater than the volumetriccapacity of the same electrical energy storage device having a graphiteelectrode. In still other embodiments, the composite material has avolumetric capacity in a lithium based energy storage device that is atleast 20% greater, at least 30% greater, at least 40% greater, at least50% greater, at least 200% greater, at least 100% greater, at least 150%greater, or at least 200% greater than the volumetric capacity of thesame electrical energy storage device having a graphite electrode.

The composite material may be prelithiated, as known in the art. Theselithium atoms may or may not be able to be separated from the carbon.The number of lithium atoms to 6 carbon atoms can be calculated bytechniques known to those familiar with the art:#Li=Q×3.6×MM/(C %×F)

wherein Q is the lithium extraction capacity measured in mAh/g betweenthe voltages of 5 mV and 2.0V versus lithium metal, MM is 72 or themolecular mass of 6 carbons, F is Faraday's constant of 96500, C % isthe mass percent carbon present in the structure as measured by CHNO orXPS.

The composite material can be characterized by the ratio of lithiumatoms to carbon atoms (Li:C) which may vary between about 0:6 and 2:6.In some embodiments the Li:C ratio is between about 0.05:6 and about1.9:6. In other embodiments the maximum Li:C ratio wherein the lithiumis in ionic and not metallic form is 2.2:6. In certain otherembodiments, the Li:C ratio ranges from about 1.2:6 to about 2:6, fromabout 1.3:6 to about 1.9:6, from about 1.4:6 to about 1.9:6, from about1.6:6 to about 1.8:6 or from about 1.7:6 to about 1.8:6. In otherembodiments, the Li:C ratio is greater than 1:6, greater than 1.2:6,greater than 1.4:6, greater than 1.6:6 or even greater than 1.8:6. Ineven other embodiments, the Li:C ratio is about 1.4:6, about 1.5:6,about 1.6:6, about 1.6:6, about 1.7:6, about 1.8:6 or about 2:6. In aspecific embodiment the Li:C ratio is about 1.78:6.

In certain other embodiments, the composite material comprises an Li:Cratio ranging from about 1:6 to about 2.5:6, from about 1.4:6 to about2.2:6 or from about 1.4:6 to about 2:6. In still other embodiments, thecomposite materials may not necessarily include lithium, but insteadhave a lithium uptake capacity (i.e., the capability to uptake a certainquantity of lithium, for example upon cycling the material between twovoltage conditions (in the case of a lithium ion half cell, an exemplaryvoltage window lies between 0 and 3 V, for example between 0.005 and 2.7V, for example between 0.005 and 1 V, for example between 0.005 and 0.8V). While not wishing to be bound by theory, it is believed the lithiumuptake capacity of the composite materials contributes to their superiorperformance in lithium based energy storage devices. The lithium uptakecapacity is expressed as a ratio of the atoms of lithium taken up by thecomposite. In certain other embodiments, the composite materialexhibiting extremely durable intercalation of lithium comprise a lithiumuptake capacity ranging from about 1:6 to about 2.5:6, from about 1.4:6to about 2.2:6 or from about 1.4:6 to about 2:6.

In certain other embodiments, the lithium uptake capacity ranges fromabout 1.2:6 to about 2:6, from about 1.3:6 to about 1.9:6, from about1.4:6 to about 1.9:6, from about 1.6:6 to about 1.8:6 or from about1.7:6 to about 1.8:6. In other embodiments, the lithium uptake capacityis greater than 1:6, greater than 1.2:6, greater than 1.4:6, greaterthan 1.6:6 or even greater than 1.8:6. In even other embodiments, theLi:C ratio is about 1.4:6, about 1.5:6, about 1.6:6, about 1.6:6, about1.7:6, about 1.8:6 or about 2:6. In a specific embodiment the Li:C ratiois about 1.78:6.

The various electrochemical states of silicon upon lithiation anddelithiation can be characterization

EXAMPLES

Example 1. Production of silicon-carbon composite material by CVI. Theproperties of the carbon scaffold (Carbon Scaffold 1) employed forproducing the silicon-carbon composite is presented in Table 3.Employing Carbon Scaffold 1, the silicon-carbon composite(Silicon-Carbon Composite 1) was produced by CVI as follows. A mass of0.2 grams of amorphous porous carbon was placed into a 2 in.×2 in.ceramic crucible then positioned in the center of a horizontal tubefurnace. The furnace was sealed and continuously purged with nitrogengas at 500 cubic centimeters per minute (ccm). The furnace temperaturewas increased at 20° C./min to 450° C. peak temperature where it wasallowed to equilibrate for 30 minutes. At this point, the nitrogen gasis shutoff and then silane and hydrogen gas are introduced at flow ratesof 50 ccm and 450 ccm, respectively for a total dwell time of 30minutes. After the dwell period, silane and hydrogen were shutoff andnitrogen was again introduced to the furnace to purge the internalatmosphere. Simultaneously the furnace heat is shutoff and allowed tocool to ambient temperature. The completed Si—C material is subsequentlyremoved from the furnace.

TABLE 3 Description of carbon scaffold employed for Example 1. CarbonSurface Pore Scaffold Area Volume % % % # (m2/g) (cm3/g) MicroporesMesopores Macropores 1 1710 0.762 93.1 6.8 0.1Example 2. Analysis of various silicon-composite materials. A variety ofcarbon scaffold materials were employed to produce a variety ofsilicon-carbon composite materials employing the CVI methodology asgenerally described in Example 1. The carbon scaffold materials werecharacterized by nitrogen sorption gas analysis to determine specificsurface area, total pore volume, and fraction of pore volume comprisingmicropores, mesopores, and macropores. The data are presented in Table4.

TABLE 4 Properites of various carbon scaffold materials. Carbon SurfacePore Scaffold Area Volume % % % # (m2/g) (cm3/g) Micropores MesoporesMacropores 1 1710 0.762 93.1 6.8 0.1 2 1697 0.77 91.9 8.0 0.1 3 17440.72 97.2 8.0 0.1 4 1581 0.832 69.1 30.9 0.1 5 1722 0.77 93.1 6.8 0.1 61710 0.817 80.1 19.9 0 7 1835 0.9 82.2 17.8 0 8 2807 1.296 85.1 14.9 0.19 1475 1.06 52.4 47.6 0 10 453 0.5 3.9 91.1 5.1 11 787 2.284 0 59.1 40.912 1746 0.7552 95 5 0

Employing these carbon scaffold materials, various silicon-carboncomposite materials employing the CVI methodology as described herein.The surface area for the silicon-carbon composites was determined. Thesilicon-carbon composites were also analyzed by TGA to determine siliconcontent and the Z. For materials exhibiting a negative Z, the Z isdescribed as zero. Silicon-carbon composite materials were also testedin half-cell coin cells. The anode for the half-cell coin cell cancomprise 60-90% silicon-carbon composite, 5-20% Na-CMC (as binder) and5-20% Super C45 (as conductivity enhancer), and the electrolyte cancomprise 2:1 ethylene carbonate:diethylene carbonate, 1 M LiPF6 and 10%fluoroethylene carbonate. The half-cell coin cells can be cycled at 25°C. at a rate of C/5 for 5 cycles and then cycled thereafter at C/10rate. The voltage can be cycled between 0 V and 0.8 V, alternatively,the voltage can be cycled between 0 V and 1.5 V. From the half-cell coincell data, the maximum capacity can be measured, as well as the averageCoulombic efficiency (CE) over the range of cycles from cycle 7 to cycle20. Physicochemical and electrochemical properties for varioussilicon-carbon composite materials are presented in Table 5.

TABLE 5 Properites of various silicon—carbon carbon scaffold materials.Silicon- Carbon Carbon Surface Si Max Average Composite Scaffold Areacontent Capacity CE # # (m2/g) (%) Z (mAh/g) (7-20) 1 1 7 45.0 0 14330.9981 2 1 7 45.4 0.4 1545 0.9980 3 1 6 45.8 0.4 1510 0.9975 4 2 33.745.8 0.43 1392 0.9993 5 3 3.06 50.1 1.0 1665 0.9969 6 2 95 42.0 1.791575 0.9970 7 3 1.96 51.3 2.0 1662 0.9974 8 2 4.5 46.4 2.29 1836 0.99879 4 140 43.1 2.40 832 0.9941 10 3 1.61 48.7 2.78 1574 0.9977 11 3 2 48.53.01 1543 0.9972 12 5 8 46.3 3.4 1373 0.9976 13 6 44 51.2 3.85 16140.9975 14 2 34 45.0 4.4 1399 0.9980 15 7 94 48.9 4.87 1455 0.9969 16 862.7 61.6 9 2056 0.9931 17 9 61 52.1 10.0 2011 0.9869 18 10 68.5 34.613.8 1006 0.9909 19 11 20 74 33.5 2463 0.9717 20 11 149 57.7 34.5 18920.9766 21 11 61.7 68.9 38.69 2213 0.9757 22 12 5 38 0.16 1037 0.9987 2312 3 37 0.12 899 0.9984A plot of the average Coulombic efficiency as a function of the Z ispresented in FIG. 1. As can seen there was dramatic increase in theaverage Coulombic efficiency for silicon-carbon samples with low Z. Inparticular, all silicon-carbon samples with Z below 5.0 (Silicon-CarbonComposite Sample 1 through Silicon-Carbon Composite Sample 15, SiliconComposite 22, and Silicon Composite 23) exhibited average Coulombicefficiency ≥0.9941, and all silicon-carbon samples with Z above 5.0(Silicon-Carbon Composite Sample 16 through Silicon-Carbon CompositeSample 21) were observed to have average Coulombic efficiency ≤0.9931.Without being bound by theory, higher Coulombic efficiency for thesilicon-carbon samples with Z<5 provides for superior cycling stabilityin full cell lithium ion batteries. Further inspection of Table revealsthe surprising and unexpected finding that the combination ofsilicon-carbon composite samples with Z<5 and also comprising carbonscaffold comprising >69.1 microporosity provides for average Coulombicefficiency ≥0.9969.

Therefore, in a preferred embodiment, the silicon-carbon compositematerial comprises a Z less than 5, for example less Z less than 4, forexample less Z less than 3, for example less Z less than 2, for exampleless Z less than 1, for example less Z less than 0.5, for example less Zless than 0.1, or Z of zero.

In certain preferred embodiments, the silicon-carbon composite materialcomprises a Z less than 5 and a carbon scaffold with >70% microporosity,for example Z less than 5 and >80% microporosity, for example Z lessthan 5 and >90% microporosity, for example Z less than 5 and >95%microporosity, for example Z less than 4 and >70% microporosity, forexample Z less than 4 and >80% microporosity, for example Z less than 4and >90% microporosity, for example Z less than 4 and >95%microporosity, for example Z less than 3 and >70% microporosity, forexample Z less than 3 and >80% microporosity, for example Z less than 3and >90% microporosity, for example Z less than 3 and >95%microporosity, for example Z less than 2 and >70% microporosity, forexample Z less than 2 and >80% microporosity, for example Z less than 2and >90% microporosity, for example Z less than 2 and >95%microporosity, for example Z less than 1 and >70% microporosity, forexample Z less than 1 and >80% microporosity, for example Z less than 1and >90% microporosity, for example Z less than 1 and >95%microporosity, for example Z less than 0.5 and >70% microporosity, forexample Z less than 0.5 and >80% microporosity, for example Z less than0.5 and >90% microporosity, for example Z less than 0.5 and >95%microporosity, for example Z less than 0.1 and >70% microporosity, forexample Z less than 0.1 and >80% microporosity, for example Z less than0.1 and >90% microporosity, for example Z less than 0.1 and >95%microporosity, for example Z of zero and >70% microporosity, for exampleZ of zero and >80% microporosity, for example Z of zero and >90%microporosity, for example Z of zero and >95% microporosity.

In certain preferred embodiments, the silicon-carbon composite materialcomprises a Z less than 5 and a carbon scaffold with >70% microporosity,and wherein the silicon-carbon composite also comprises 15%-85% silicon,and surface area less than 100 m2/g, for example Z less than 5 and >70%microporosity, and wherein the silicon-carbon composite also comprises15%-85% silicon, and surface area less than 50 m2/g, for example Z lessthan 5 and >70% microporosity, and wherein the silicon-carbon compositealso comprises 15%-85% silicon, and surface area less than 30 m2/g, forexample Z less than 5 and >70% microporosity, and wherein thesilicon-carbon composite also comprises 15%-85% silicon, and surfacearea less than 10 m2/g, for example Z less than 5 and >70%microporosity, and wherein the silicon-carbon composite also comprises15%-85% silicon, and surface area less than 5 m2/g, for example Z lessthan 5 and >80% microporosity, and wherein the silicon-carbon compositealso comprises 15%-85% silicon, and surface area less than 50 m2/g, forexample Z less than 5 and >80% microporosity, and wherein thesilicon-carbon composite also comprises 15%-85% silicon, and surfacearea less than 30 m2/g, for example Z less than 5 and >80%microporosity, and wherein the silicon-carbon composite also comprises15%-85% silicon, and surface area less than 10 m2/g, for example Z lessthan 5 and >80% microporosity, and wherein the silicon-carbon compositealso comprises 15%-85% silicon, and surface area less than 5 m2/g, forexample Z less than 5 and >90% microporosity, and wherein thesilicon-carbon composite also comprises 15%-85% silicon, and surfacearea less than 50 m2/g, for example Z less than 5 and >90%microporosity, and wherein the silicon-carbon composite also comprises15%-85% silicon, and surface area less than 30 m2/g, for example Z lessthan 5 and >90% microporosity, and wherein the silicon-carbon compositealso comprises 15%-85% silicon, and surface area less than 10 m2/g, forexample Z less than 5 and >90% microporosity, and wherein thesilicon-carbon composite also comprises 15%-85% silicon, and surfacearea less than 5 m2/g, for example Z less than 5 and >95% microporosity,and wherein the silicon-carbon composite also comprises 15%-85% silicon,and surface area less than 50 m2/g, for example Z less than 5 and >95%microporosity, and wherein the silicon-carbon composite also comprises15%-85% silicon, and surface area less than 30 m2/g, for example Z lessthan 5 and >95% microporosity, and wherein the silicon-carbon compositealso comprises 15%-85% silicon, and surface area less than 10 m2/g, forexample Z less than 5 and >95% microporosity, and wherein thesilicon-carbon composite also comprises 15%-85% silicon, and surfacearea less than 5 m2/g.

In certain preferred embodiments, the silicon-carbon composite materialcomprises a Z less than 5 and a carbon scaffold with >70% microporosity,and wherein the silicon-carbon composite also comprises 30%-60% silicon,and surface area less than 100 m2/g, for example Z less than 5 and >70%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 50 m2/g, for example Z lessthan 5 and >70% microporosity, and wherein the silicon-carbon compositealso comprises 30%-60% silicon, and surface area less than 30 m2/g, forexample Z less than 5 and >70% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 10 m2/g, for example Z less than 5 and >70%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 5 m2/g, for example Z lessthan 5 and >80% microporosity, and wherein the silicon-carbon compositealso comprises 30%-60% silicon, and surface area less than 50 m2/g, forexample Z less than 5 and >80% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 30 m2/g, for example Z less than 5 and >80%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 10 m2/g, for example Z lessthan 5 and >80% microporosity, and wherein the silicon-carbon compositealso comprises 30%-60% silicon, and surface area less than 5 m2/g, forexample Z less than 5 and >90% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 50 m2/g, for example Z less than 5 and >90%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 30 m2/g, for example Z lessthan 5 and >90% microporosity, and wherein the silicon-carbon compositealso comprises 30%-60% silicon, and surface area less than 10 m2/g, forexample Z less than 5 and >90% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 5 m2/g, for example Z less than 5 and >95% microporosity,and wherein the silicon-carbon composite also comprises 30%-60% silicon,and surface area less than 50 m2/g, for example Z less than 5 and >95%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 30 m2/g, for example Z lessthan 5 and >95% microporosity, and wherein the silicon-carbon compositealso comprises 30%-60% silicon, and surface area less than 10 m2/g, forexample Z less than 5 and >95% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 5 m2/g.

Example 3. dV/dQ for various silicon-composite materials. Differentialcapacity curve (dQ/dV vs Voltage) is often used as a non-destructivetool to understand the phase transition as a function of voltage inlithium battery electrodes (M. N. Obrovac et al. Structural Changes inSilicon Anodes during Lithium Insertion/Extraction, Electrochemical andSolid-State Letters, 7 (5) A93-A96 (2004); Ogata, K. et al. Revealinglithium-silicide phase transformations in nano-structured silicon-basedlithium ion batteries via in situ NMR spectroscopy. Nat. Commun.5:3217). Differential capacity plots presented here is calculated fromthe data obtained using galvanostatic cycling at 0.1 C rate between 5 mVto 0.8V in a half-cell coin cell at 25° C. Typical differential capacitycurve for a silicon-based material in a half-cell vs lithium can befound in many literature references (Loveridge, M. J. et al. TowardsHigh Capacity Li-Ion Batteries Based on Silicon-Graphene CompositeAnodes and Sub-micron V-doped LiFePO4 Cathodes. Sci. Rep. 6, 37787; doi:10.1038/srep37787 (2016); M. N. Obrovac et al. Li15Si4 Formation inSilicon Thin Film Negative Electrodes, Journal of The ElectrochemicalSociety, 163 (2) A255-A261 (2016); Q. Pan et al. Improvedelectrochemical performance of micro-sized SiO-based composite anode byprelithiation of stabilized lithium metal powder, Journal of PowerSources 347 (2017) 170-177). First cycle lithiation behavior isdependent on the crystallinity of the silicon and oxygen content amongother factors.

After first cycle, previous amorphous silicon materials in the artexhibit two specific phase transition peaks in the dQ/dV vs V plot forlithiation, and correspondingly two specific phase transition peaks inthe dQ/dV vs V plot for delithiation. For lithiation, one peakcorresponding to lithium-poor Li—Si alloy phase occurs between 0.2-0.4 Vand another peak corresponding to a lithium-rich Li—Si alloy phaseoccurs below 0.15 V. For delithiation, one delithiation peakcorresponding to the extraction of lithium occurs below 0.4 V andanother peak occurs between 0.4 V and 0.55 V. If the Li15Si4 phase isformed during lithiation, it is delithiated at −0.45V and appears as avery narrow sharp peak.

FIG. 2 depicts the dQ/dV vs Voltage curve for cycle 2 for thesilicon-carbon composite material corresponding to Silicon-CarbonComposite 3 from Example 1. Silicon-Carbon Composite 3 comprises a Z of0.4. For ease of identification, the plot is divided into regimes I, II,II, IV, V, and VI. Regimes I (0.8 V to 0.4 V), II (0.4 V to 0.15 V), III(0.15 V to 0 V) comprise the lithiation potentials and Regimes IV (0 Vto 0.4 V), V (0.4 V to 0.55 V), VI (0.55 V to 0.8 V) comprise thedelithiation potential. As described above, previous amorphoussilicon-based materials in the art exhibit phase-transition peaks fortwo regimes (Regime II and Regime III) in the lithiation potential andtwo regimes (Regime IV and Regime V) in the dethiation potentials.

As can be seen in FIG. 2, the dQ/dV vs Voltage curve reveals surprisingand unexpected result that Silicon-Carbon Composite 3, which comprises aZ of 0.4, comprises two additional peaks in the dQ/dV vs Voltage curve,namely Regime I in the lithiation potential and Regime VI in thedelithiation potential. All 6 peaks are reversible and observed in thesubsequent cycles as well, as shown in FIG. 3.

Without being bound by theory, such trimodal behavior for the dQ/dV vs Vcurve is novel, and likewise reflects a novel form of silicon.

Notably, the novel peaks observed in Regime I and Regime VI are morepronounced in certain scaffold matrixes and completely absent in otherssamples illustrating the prior art (silicon-carbon composite sampleswith Z>5, see explanation and table below).

FIG. 4 presents the dQ/dV vs V curve for Silicon-Carbon Composite 3,wherein the novel peaks in Regime I and Regime VI are evident, incomparison to Silicon-Carbon Composite 20, Silicon-Carbon Composite 21,and Silicon-Carbon Composite 19, all three of which comprise Z>5 andwhose dQ/dV vs V curves are devoid of the any peaks in Regime I andRegime VI.

Without being bound by theory, these novel peaks observed in Regime Iand Regime VI relate to the properties of the silicon impregnated intothe porous carbon scaffold, i.e., related to the interactions betweenand among the properties of the porous carbon scaffold, the siliconimpregnated into the porous carbon scaffold via CVI, and lithium. Inorder to provide a quantitative analysis, we herein define the parameterφ, which is calculated as the normalized peak I with respect to peak IIIas:φ=(Max peak height dQ/dV in Regime I)/(Max peak height dQ/dV in RegimeIII)where dQ/dV is measured in a half-cell coin cell, and regime I is0.8V-0.4V and Regime III is 0.15V-0V; the half-cell coin cell isproduced as known in the art. If the Si—C sample shows peaks associatedwith graphite in regime III of the differential curve, it is omitted infavor of Li—Si related phase transition peaks for the calculation of Dfactor. For this example, the half-cell coin cell comprises an anodecomprising 60-90% silicon-carbon composite, 5-20% SBR-Na-CMC, and 5-20%Super C45. An example for φ calculation is shown in FIG. 5 forSilicon-Carbon Composite 3. In this instance, the maximum peak height inthe regime I is −2.39 and is found at voltage 0.53V. Similarly, maximumpeak height in regime III is −9.71 at 0.04V. In this instance, φ can becalculated using the above formula, yielding φ=−2.39/−9.71=0.25. Thevalue of φ was determined from the half-cell coin cell data for thevarious silicon-carbon composites presented in Example 2. These data aresummarized in Table 6.

TABLE 6 Properites of various silicon—carbon carbon scaffold materials.Silicon- Carbon Carbon Surface Si Average Composite Scaffold Areacontent CE # # (m2/g) (%) Z (7-20) φ 1 1 7 45.0 0 0.9981 0.24 2 1 7 45.40.4 0.9980 0.24 3 1 6 45.8 0.4 0.9975 0.25 4 2 33.7 45.8 0.43 0.99930.20 5 3 3.06 50.1 1.0 0.9969 0.18 6 2 95 42.0 1.79 0.9970 0.20 7 3 1.9651.3 2.0 0.9974 0.18 8 2 4.5 46.4 2.29 0.9987 0.19 9 4 140 43.1 2.400.9941 0.13 10 3 1.61 48.7 2.78 0.9977 0.19 11 3 2 48.5 3.01 0.9972 0.1912 5 8 46.3 3.4 0.9976 0.20 13 6 44 51.2 3.85 0.9975 0.13 14 2 34 45.04.4 0.9980 0.19 15 7 94 48.9 4.87 0.9969 0.15 16 8 62.7 61.6 9 0.99310.11 17 9 61 52.1 10.0 0.9869 0.00 18 10 68.5 34.6 13.8 0.9909 0.00 1911 20 74 33.5 0.9717 0.00 20 11 149 57.7 34.5 0.9766 0.00 21 11 61.768.9 38.69 0.9757 0.00

The data in Table 6 reveal an unexpected relationship between decreasingZ and increasing φ. All silicon-carbon composites with Z<5 had φ≥0.12,and all silicon-carbon composites with Z>5 had φ≥0.11, indeed, in 5 outof 6 cases for silicon-carbon composites with Z>5 had φ=0. Thisrelationship is also evidenced in FIG. 6. Without being bound by theory,silicon materials comprising φ≥0.12 correspond to a novel form ofsilicon. Alternatively, silicon materials comprising φ≥0 correspond to anovel form of silicon. The silicon-carbon composite material comprisingsilicon comprising φ≥0.12 correspond to a novel silicon-carbon compositematerial. Alternatively, silicon-carbon composite materials comprisingφ>0 corresponds to a novel silicon-carbon composite material.

In certain embodiments, the silicon-carbon composite comprises a φ≥0.12,φ≥0.13, φ≥0.14, φ≥0.15, φ≥0.16, φ≥0.17, φ≥0.18, φ≥0.19, φ≥0.20, φ≥0.21,φ≥0.22, φ≥0.23, φ≥0.24 or φ≥0.25.

In certain embodiments, the silicon-carbon composite material comprisesa Z less than 5 and a carbon scaffold with >70% microporosity, andwherein the silicon-carbon composite also comprises 30%-60% silicon, andsurface area less than 100 m2/g, and φ≥0.12, for example Z less than 5and >70% microporosity, and wherein the silicon-carbon composite alsocomprises 30%-60% silicon, and surface area less than 50 m2/g, andφ≥0.12, for example Z less than 5 and >70% microporosity, and whereinthe silicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 30 m2/g, and φ≥0.12, for example Z less than 5 and >70%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 10 m2/g, and φ≥0.12, forexample Z less than 5 and >70% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 5 m2/g, and φ≥0.12.

In certain embodiments, the silicon-carbon composite material comprisesa Z less than 5 and a carbon scaffold with >80% microporosity, andwherein the silicon-carbon composite also comprises 30%-60% silicon, andsurface area less than 100 m2/g, and φ≥0.12, for example Z less than 5and >80% microporosity, and wherein the silicon-carbon composite alsocomprises 30%-60% silicon, and surface area less than 50 m2/g, andφ≥0.12, for example Z less than 5 and >80% microporosity, and whereinthe silicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 30 m2/g, and φ≥0.12, for example Z less than 5 and >80%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 10 m2/g, and φ≥0.12, forexample Z less than 5 and >80% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 5 m2/g, and φ≥0.12.

In certain embodiments, the silicon-carbon composite material comprisesa Z less than 5 and a carbon scaffold with >90% microporosity, andwherein the silicon-carbon composite also comprises 30%-60% silicon, andsurface area less than 100 m2/g, and φ≥0.12, for example Z less than 5and >90% microporosity, and wherein the silicon-carbon composite alsocomprises 30%-60% silicon, and surface area less than 50 m2/g, andφ≥0.12, for example Z less than 5 and >90% microporosity, and whereinthe silicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 30 m2/g, and φ≥0.12, for example Z less than 5 and >90%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 10 m2/g, and φ≥0.12, forexample Z less than 5 and >90% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 5 m2/g, and φ≥0.12.

In certain embodiments, the silicon-carbon composite material comprisesa Z less than 5 and a carbon scaffold with >95% microporosity, andwherein the silicon-carbon composite also comprises 30%-60% silicon, andsurface area less than 100 m2/g, and φ≥0.12, for example Z less than 5and >95% microporosity, and wherein the silicon-carbon composite alsocomprises 30%-60% silicon, and surface area less than 50 m2/g, andφ≥0.12, for example Z less than 5 and >95% microporosity, and whereinthe silicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 30 m2/g, and φ≥0.12, for example Z less than 5 and >95%microporosity, and wherein the silicon-carbon composite also comprises30%-60% silicon, and surface area less than 10 m2/g, and φ≥0.12, forexample Z less than 5 and >95% microporosity, and wherein thesilicon-carbon composite also comprises 30%-60% silicon, and surfacearea less than 5 m2/g, and φ≥0.12.

EXPRESSED EMBODIMENTS

Embodiment 1. A material exhibiting φ>0, φ=(Max peak height dQ/dV inRegime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dV ismeasured in a half-cell coin cell, and regime I is 0.8V-0.4V and RegimeIII is 0.15V-0V.

Embodiment 2. A material exhibiting φ>0.12, —φ=(Max peak height dQ/dV inRegime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dV ismeasured in a half-cell coin cell, and regime I is 0.8V-0.4V and RegimeIII is 0.15V-0V.

Embodiment 3. A silicon-carbon composite material exhibiting φ>0, φ=(Maxpeak height dQ/dV in Regime I)/(Max peak height dQ/dV in Regime III),wherein dQ/dV is measured in a half-cell coin cell, and regime I is0.8V-0.4V and Regime III is 0.15V-0V.

Embodiment 4. A silicon-carbon composite material exhibiting φ>0.12,φ=(Max peak height dQ/dV in Regime I)/(Max peak height dQ/dV in RegimeIII), wherein dQ/dV is measured in a half-cell coin cell, and regime Iis 0.8V-0.4V and Regime III is 0.15V-0V.

Embodiment 5. A silicon-carbon composite material comprising a Z<5 andφ>0, φ=(Max peak height dQ/dV in Regime I)/(Max peak height dQ/dV inRegime III), wherein dQ/dV is measured in a half-cell coin cell, andregime I is 0.8V-0.4V and Regime III is 0.15V-0V.Embodiment 6. A silicon-carbon composite material comprising a Z<5 andφ>0.12, φ=(Max peak height dQ/dV in Regime I)/(Max peak height dQ/dV inRegime III), wherein dQ/dV is measured in a half-cell coin cell, andregime I is 0.8V-0.4V and Regime III is 0.15V-0V.Embodiment 7. A silicon-carbon composite material comprising a Z<5,surface area <100 m2/g, and >0, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 8. A silicon-carbon composite material comprising a Z<5,surface area <100 m2/g, and φ≥0.12, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 9. A silicon-carbon composite material comprising a Z<5,surface area <50 m2/g, and φ≥=(Max peak height dQ/dV in Regime I)/(Maxpeak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 10. A silicon-carbon composite material comprising a Z<5,surface area <50 m2/g, and φ≥0.12, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 11. A silicon-carbon composite material comprising a Z<5,surface area <30 m2/g, and φ>0, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 12. A silicon-carbon composite material comprising a Z<5,surface area <30 m2/g, and φ≥0.12, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 13. A silicon-carbon composite material comprising a Z<5,surface area <10 m2/g, and φ≥0, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 14. A silicon-carbon composite material comprising a Z<5,surface area <10 m2/g, and φ≥0.12, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 15. A silicon-carbon composite material comprising a Z<5,surface area <5 m2/g, and φ>0, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 16. A silicon-carbon composite material comprising a Z<5,surface area <5 m2/g, and φ≥0.12, φ=(Max peak height dQ/dV in RegimeI)/(Max peak height dQ/dV in Regime III), wherein dQ/dV is measured in ahalf-cell coin cell, and regime I is 0.8V-0.4V and Regime III is0.15V-0V.Embodiment 17. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <50 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 18. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <50 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 19. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 20. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 21. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 22. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 23. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 24. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V.Embodiment 25. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <50 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 26. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <50 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 27. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 28. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 29. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 30. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 31. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 32. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >70% microporosity.Embodiment 33. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >80% microporosity.Embodiment 34. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >80% microporosity.Embodiment 35. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >80% microporosity.Embodiment 36. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >80% microporosity.Embodiment 37. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >80% microporosity.Embodiment 38. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >80% microporosity.Embodiment 39. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >90% microporosity.Embodiment 40. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and >0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >90% microporosity.Embodiment 41. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >90% microporosity.Embodiment 42. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >90% microporosity.Embodiment 43. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >90% microporosity.Embodiment 44. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >90% microporosity.Embodiment 45. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >95% microporosity.Embodiment 46. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <30 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >95% microporosity.Embodiment 47. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >95% microporosity.Embodiment 48. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <10 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >95% microporosity.Embodiment 49. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >95% microporosity.Embodiment 50. A silicon-carbon composite comprising 30% to 60% siliconby weight, a Z<5, surface area <5 m2/g, and φ>0.12, φ=(Max peak heightdQ/dV in Regime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dVis measured in a half-cell coin cell, and regime I is 0.8V-0.4V andRegime III is 0.15V-0V, and a carbon scaffold comprising a pore volume,wherein the pore volume comprises >95% microporosity.Embodiment 51. The silicon-carbon composite of any of the embodimentsfrom Embodiment 1 to Embodiment 50 wherein the silicon-carbon compositecomprises a Dv50 between 5 nm and 20 microns.Embodiment 52. The silicon-carbon composite of any of the embodimentsfrom Embodiment 1 to Embodiment 51 wherein the silicon-carbon compositecomprises a capacity of greater than 900 mA/g.Embodiment 53. The silicon-carbon composite of any of the embodimentsfrom Embodiment 1 to Embodiment 51 wherein the silicon-carbon compositecomprises a capacity of greater than 1300 mA/g.Embodiment 54. The silicon-carbon composite of any of the embodimentsfrom Embodiment 1 to Embodiment 51 wherein the silicon-carbon compositecomprises a capacity of greater than 1600 mA/g.Embodiment 55. An energy storage device comprising a silicon-carboncomposite described by any of the embodiments from Embodiment 1 toEmbodiment 53.Embodiment 56. A lithium ion battery comprising a silicon-carboncomposite described by any of the embodiments from Embodiment 1 toEmbodiment 53.

From the foregoing it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

The invention claimed is:
 1. A silicon-carbon composite comprising: a. acarbon scaffold comprising a pore volume, wherein the pore volumecomprises greater than 80% microporosity; b. a silicon content of 30% to60% by weight; c. a surface area less than 30 m2/g; and d. a φ ofgreater than or equal to 0.12, wherein φ=(Max peak height dQ/dV inRegime I)/(Max peak height dQ/dV in Regime III), wherein dQ/dV ismeasured in a half-cell coin cell, and Regime I is 0.8V-0.4V and RegimeIII is 0.15V-0V.
 2. The silicon-carbon composite of claim 1, wherein thepore volume comprises greater than 90% microporosity.
 3. Thesilicon-carbon composite of claim 2, wherein the pore volume comprisesgreater than 95% microporosity.
 4. The silicon-carbon composite of claim3, comprising a surface area less than 10 m2/g.
 5. The silicon-carboncomposite of claim 3, comprising a surface area less than 5 m2/g.
 6. Thesilicon-carbon composite of claim 5, comprising a silicon content of 40%to 60% by weight.
 7. The silicon-carbon composite of claim 2, comprisinga surface area less than 10 m2/g.
 8. The silicon-carbon composite ofclaim 2, comprising a surface area less than 5 m2/g.
 9. Thesilicon-carbon composite of claim 2, comprising a silicon content of 40%to 60% by weight.
 10. The silicon-carbon composite of claim 1,comprising a surface area less than 10 m2/g.
 11. The silicon-carboncomposite of claim 10, comprising a silicon content of 40% to 60% byweight.
 12. The silicon-carbon composite of claim 1, comprising asurface area less than 5 m2/g.
 13. The silicon-carbon composite of claim1, comprising a silicon content of 40% to 60% by weight.
 14. The siliconcarbon composite of claim 1, wherein the y is greater than or equal to0.13.
 15. The silicon carbon composite of claim 1, wherein the y isgreater than or equal to 0.14.
 16. The silicon carbon composite of claim1, wherein the silicon-carbon composite comprises a Dv50 ranging from 5nm to 20 microns.
 17. The silicon carbon composite of claim 1, whereinthe silicon-carbon composite comprises a capacity of greater than 900mA/g.
 18. The silicon-carbon composite of claim 1, further comprisinglithium.
 19. An electrode comprising the silicon-carbon composite ofclaim
 1. 20. An energy storage device comprising the silicon-carboncomposite of claim
 1. 21. The energy storage device of claim 20, whereinthe energy storage device is a Li ion battery.